Inside Great Shefford Observatory

Confirming the recovery of Comet P/2006 T1 (Levy)

2011-12-19T00:59:00.001Z

Comet P/2006 T1 (Levy), due back to the Sun's neighbourhood in mid-January 2012, its first return to the Sun following its discovery in 2006 was eventually recovered by Richard Kowalski from the Mt. Lemon Survey early on 17 Dec 2011 during a search of the object's entire uncertainty region.

It was over 2° from the predicted position at the time and magnitude +19, about 9 magnitudes fainter than predicted, based on its brightness during the 2006 apparition, though it is thought that the comet underwent a brightness outburst just before being discovered.

The recovery was confirmed by further positional measurements from observatories Farra d'Isonzo (595) and Great Shefford (J95), both observatories noting the object as diffuse and with an elongated coma or tail pointing to the North-East (upper left in the image below).

Images taken from Great Shefford Observatory of the comet at its 2006 discovery apparition can be found here.

2011 November notes

2011-12-09T00:04:00.007Z

Poor weather in the first half of November (that stopped the very close fly-by of 2005 YU55 from being observed from Great Shefford) was replaced by a decent last two weeks and plenty of newly discovered NEOs were found to be in need of observation, although a fair number of these were rather faint.

However, there were a few close passes observed and probably the best of those were by 2011 WP4 and 2011 WQ4. My last sighting of 2011 WP4 was on the morning of Nov 23 at mag +17.6 with it moving almost due south at 48"/min. At that time it was just over 3 Lunar Distances (LD) from Earth. Two other observatories observed it in the few hours following but no one reported it at its closest just over 1 day later when it had approached to within 1.5 LD and was moving 5 times faster but had reached high southerly declinations of -60 to -70 degrees. 2011 WQ4, although a similar absolute magnitude to 2011 WP4 (H=+27.4 vs H=+27.2 for WP4, equating to likely diameters in the range of 8-13 meters) was always a fainter target and only approached to 2 LD. It was also last seen on the morning of Nov 23, heading out from its close approach a day and a half earlier but by then was only mag +19 and moving at 55"/min made it a much harder target than 2011 WP4 had been.

At 10pm on the night of Nov 17th I received an email from Michel Ory (discoverer of Comet P/2008 Q2) requesting help to try and recover a fast moving 19th mag. object that Claudine Rinner had discovered two nights earlier from station J43 with a 0.5-m f/3 reflector (she would go on to discover Comet P/2011 W2 less than 2 weeks later with the same instrument). With only three positions spanning just 41 minutes from Nov 15th, the uncertainty in the position predicted by FindOrb for Nov 17th was expected to be fairly large and so a number of fields would need to be taken to stand any chance of recovery. Although Michel had sent the positions into the Minor Planet Center, the object had not yet appeared on the NEO Confirmation page (NEOCP). I started taking images for it within the hour, but already it was getting low in the southwest, the altitude of the field was only 27 degrees and getting lower but even more of a problem was thickening cloud coming in from the west. I managed to search for nearly 45 minutes before being completely clouded out but could not positively identify anything, especially difficult with the poor quality, cloud affected images.

The next night was clear and so I started searching again for the object, earlier in the evening and in better conditions than the night before. By now it was listed on the NEOCP, together with an uncertainty map showing its likely location was expected to be anywhere within a strip of sky over 2.5 degrees long. After 1h 45mins I eventually found the telltale expected movement in blinked images about 3/4 degree ahead of the NEOCP nominal predicted position. To help other observers, at 10:30pm I posted a comment on the NEOCP Blog (http://minorplanetcenter.net/NEOCPblog/) stating where I'd found it and about 15 minutes later, a set of positions from the Catalina Sky Survey Mt. Lemmon telescope (station code G96) were posted from images taken some 18 hours earlier.

In the meantime I had used FindOrb to improve the orbital elements, combining the discovery positions with those I had just measured and worked out an ephemeris for the previous night. With the accurate ephemeris and much improved values for the rate of motion, I was able to re-stack the images from the night before and managed to identify weak images of the object. These were quickly measured and both nights of measures sent in to the Minor Planet Center and by 10:52pm the Minor Planet Center announced the new discovery as Amor object 2011 VP12 in MPEC 2011-W18, containing the discovery positions from J43 together with those from G96 and my two nights. Congratulations to Claudine on this discovery as well as for P/2011 W2!

On Nov 26, NASA launched the Mars Science Laboratory (MSL) on top of an Atlas V rocket and, using an ephemeris from the JPL Horizons web page available from http://ssd.jpl.nasa.gov/horizons.cgi I picked it up on the morning of Nov 28 at mag 16.8-17.0, moving at a fairly gentle 5"/min. The next day a 16th mag object was added to the NEOCP with very similar RA and Dec to where I had observed MSL the night before and moving in the same direction with similar speed. It was quickly determined however that this object was NOT MSL, but rather the Centaur second stage of the Atlas V rocket, about 3/4 degree away from the MSL spacecraft. The Centaur stage is used twice, once to achieve a low Earth orbit after launch, then again to take the MSL out of Earth orbit and accelerate it towards Mars and although not part of the experiment is accompanying MSL on its journey to Mars. I imaged both the MSL and the Centaur 2nd stage on the morning of Nov 30th and by then MSL had more than doubled its distance from Earth since my first observation, 2.8 LDs compared to 1.3 LDs two days earlier and was also a magnitude fainter than before at +18.1. The Centaur stage was much brighter than MSL, maybe by a magnitude or more and was also varying rapidly in brightness, very obviously changing between consecutive images, in marked contrast to the steady light from the more stable MSL spacecraft.

2011 September notes

2011-10-05T21:00:00.013+01:00

A big improvement over recent months, September ended with a remarkable and record breaking heatwave in the UK and more than half the nights in the month being at least partially usable at Great Shefford, though fog and mist stopped work several hours before dawn on a number of occasions.

After a quiet summer, both PANSTARRS and the Catalina Sky Survey (CSS) telescopes were in full survey mode, looking for new Near Earth Objects and astrometry was contributed for 43 of the objects posted on the NEO Confirmation Page.

PANSTARRS picked up 2011 SP25 on September 20th, relatively faint at mag +20 and slow moving, I observed it 2 nights later and measured it at (red) mag +19.7. It is not a NEO and at the time of writing (Oct. 5th) there are now two weeks of astrometry available and the elements show it to be in a highly eccentric retrograde Halley-type orbit with period 89 years and perihelion at 2.27 AU due this coming November. It looked completely stellar in my images and will probably stay that way, but may be worth keeping an eye on in the next couple of months.

A couple of moderately close NEO passes were well observed, 2011 LJ19, discovered back in June by CSS came closest mid-month, at about 17 Lunar Distances (LD) and maintained 16th mag or brighter for about 2 weeks. A CSS discovery from September, 2011 SR5, passed about 22 LD towards the end of the month and peaked at mag +16 for about 5 days, reaching a speed against the sky slightly faster than 2011 LJ19 at 35"/min.

The closest observed approach though was 2011 SE58, a very faint mag +20.8 discovery made early on September 23 by the Spacewatch team using the 1.8-m reflector on Kitt Peak, when it was moving slowly at 0.8"/min. Spacewatch observed it again the next night by which time it had tripled in speed and was about 0.7 mags brighter, closing in fast at a range of about 14 LD.

I observed it 11 hours later on September 24 at 21:00 UT and found it more than a magnitude brighter at +18.7 and moving at 4"/min. Its distance had approximately halved to 8 LD in that time and a very close approach to 0.6 LD was predicted for September 27.1 UT. The next night was cloudy in Great Shefford but the night of the close approach started out clear. By 23:00 UT 2011 SE58 had risen to an altitude of 14 degrees, just high enough in the east to clear my house roof but it was moving so fast due east and still accelerating that it almost kept pace with the Earth's diurnal motion and stayed in approximately the same place just above the rooftop, edging in azimuth towards the south for the next hour, until mist came down and stopped any further observation. Although registering between mags +14-15 it was moving so fast and at a low altitude that it was unfortunately never recorded strongly enough for any accurate photometry to be attempted.

Here 2011 SE58 is seen passing from west to east through the 18'x18' field of view in less than 2 minutes

When first picked up that night it was moving at 480"/min at 0.80 LD and when last recorded 58 minutes later had accelerated to 600"/min, had approached to 0.72LD and moved a total of 9 degrees against the sky background. The Minor Planet Center Daily Orbit Update published the next morning included the measures I had made that night and also included some pre-discovery PANSTAARS astrometry from 2 days before the Spacewatch discovery observations, when it was 22nd magnitude and had only moved 9" in the hour it was under observation, quite a change in a week!

2011 August notes: An amateur discovered tumbling NEO

2011-09-09T03:08:00.001+01:00

August continued the poor run of weather from July and most of the time it was a case of making the best of what clear sky there was.

One opportunity came early in the morning on August 9th when a new discovery was posted on the NEO Confirmation Page, eventually designated as 2011 PE2, this one picked up by the amateur run La Sagra Sky Survey in Spain. The discovery images were from 24 hours earlier which was quite unusual, often La Sagra post their discoveries in near real-time. Jaime Nomen from the survey mentioned later that their reduction software had crashed during the previous evening and those images that had not been processed at the time were put into the queue for the next night, so it was only detected a day later.

Because of the delay the positional uncertainty was growing, with the Minor Planet Center's uncertainty map indicating the likely area it might be found in was 1.75 degrees long. I eventually picked it up 20' from the nominal prediction and then followed it for 20 minutes to get enough images to measure astrometry to send to the MPC. The ephemeris indicated it should be about mag +18.3 but during that 20 minutes it could be seen to vary in brightness from barely visible to very obvious within about 10 minutes. Because of this, I decided to continue to follow it until dawn to try and obtain a lightcurve, ending up with nearly three hours of measurements and showing the total variation to be very large at about 2 magnitudes (a factor of 6). 2011 PE2 was about at its brightest when discovered and on subsequent nights had already faded too much for any more useful photometry to be obtained.

Canopus was used to reduce the brightness measurements obtained that first night and to plot a lightcurve. Although the rises and falls from max. to min. in approx 10 minutes that were noticed at the time the images were taken were visible, the variations were not regular, indicating that it may not be simply rotating in one axis, but probably tumbling. In the diagram below, "beating" can be seen in the maxima and minima as two competing periods cause constructive and destructive interference to the overall curve, indeed at about 0.57 on the x-axis a minimum is almost completely absent.

Solving for a single period gives a value of 43.8 minutes for the main variation (so 11 minutes between each maxima and minima). However, the second period has not yet been satisfactorily determined and so the final value of the main period is still undetermined and could be somewhat different to that given above.

Raw (unfolded) lightcurve of 2011 PE2 from 348 data points obtained 2011 Aug. 09 00:14-03:08 UT

Bright Supernova 2011fe in galaxy M101

2011-08-28T00:03:00.022+01:00

Discovered automatically by the The Palomar Transient Factory on August 24 at magnitude 17, this was quickly determined to be a very young type 1a supernova, expected to brighten by possibly 6 magnitudes within the next week or two.

The animation below consists of two frames, the first taken on 2003 Jan 28 using a 0.3-m telescope, before the supernova appeared and the second on 2011 Aug 27 using a 0.4-m telescope, with the supernova at magnitude +13.0. This image was obtained during a 4 minute gap with the object passing between trees, when M101 was almost at its lowest point over the north horizon, poor weather preventing any attempt in better circumstances.

The Sky At Night comes to Great Shefford

2011-08-19T03:03:00.002+01:00

The BBC's Sky at Night team visited Great Shefford Observatory on July 6th and filmed a short interview following the very close approach of NEO 2011 MD at the end of June (see the June and July notes).

The interview was included in the program "Dawn at Vesta" and was first transmitted in the early hours of Monday 8th August on BBC1.

Watch the interview with Paul Abel here:

2011 July notes: 2011 MD and recovering 2000 CP101

2011-08-09T01:48:00.006+01:00

Early in July the remarkable NEO 2011 MD was still under observation following its exceedingly close pass to just 7600 miles above the Earth's surface at the end of June. It was visible at high northerly declinations before and after the near-miss only because of the severe perturbations caused by the Earth's gravity, putting a 130° kink in its trajectory (see the JPL news story here)

The final images I obtained were taken during the early morning of July 3 with 2011 MD moving relatively slowly at 5"/min in Cassiopeia in a very rich Milky Way star field, near the border with Cepheus and Lacerta. Even though more than 5 days after the close approach, 2011 MD was still only 2.5 Lunar Distances from Earth and with the object at nearly 20th magnitude this combination caused a rather unusual problem when trying to measure positions. Plenty of images needed to be taken to register a 20th mag target and so I took 200 x 20-second exposures between 00:37 and 02:07 UT, before twilight started to interfere. However, because of the rich star field, wherever the asteroid passed too close to stars many of the images would have to be discarded. Normally, this process is time consuming but straightforward, involving identifying the stars on a line from the first to the last ephemeris position and estimating which of the corresponding images should be left out before stacking the remaining images together to enhance the feeble light from the faint asteroid.

When I did this and started stacking various combinations of images with Astrometrica I kept on finding the faint image of the NEO was contaminated with star trails, which should not have been happening if I had properly identified the images to discard.

The cause of the problem was that the object was so close to the Earth, but moving so slowly against the sky that the Earth's diurnal rotation was causing the apparent track of the NEO to be significantly curved. The image shows the difference between the more usual straight track and the actual curved track.

Track of 2011 MD on 2011 July 3.07 UT, 9'x9' field of view

Armed with the new track and this time leaving out the correct images I managed to get three sets of images stacked and measured and sent off to the Minor Planet Center. The position measured from the final stack, shown here was the last reported sighting of 2011 MD received by the MPC.

Later in the month I searched for NEO 2000 CP101, discovered by LINEAR on 2000 Feb 10 and observed for the next 30 days but not seen in the 11 years since. By July 24 it was expected to be 18th magnitude but the 3-sigma uncertainty area was a daunting +/- 21 degrees long, stretching east and west from the nominal prediction, far too big to sensibly search the whole area using my 0.3 degree field of view.

In an effort to try and reduce the scale of the search I retrieved all the original astrometry via the Minor Planet Center's MPCOBS facility at http://www.minorplanetcenter.net/db_search and then used FindOrb, brutally filtering out any observations that had residuals bigger than 0.5" and then producing an ephemeris from the resultant orbit. The MPC prediction by contrast was much more lenient and included most of the original observations. My ephemeris placed the object a couple of degrees to the east of the MPC prediction and hoping for the best I started searching from that point, working outwards both to the east and west.

I started at dusk and after 4.5 hours, covering 13 fields of view, I eventually picked up the telltale motion of 2000 CP101 just before dawn. It turned out to be 3.7 degrees east of the MPC prediction. After obtaining confirming images the following night, the recovery was announced in Minor Planet Circular MPEC 2011-O29.

The 13 fields taken during the search for 2000 CP101, Delphinus is at top left and Altair at lower right.
Graphic generated using SkyMap Pro 9

Confirming the discovery of close approach asteroid 2011 MD

2011-06-28T01:46:00.004+01:00

The Minor Planet Center (MPC) added two new LINEAR discoveries to the NEO Confirmation page (NEOCP) just after 01am UT on 23 June while I was taking images of another object discovered a day and a half earlier by the SPACEWATCH team (which would eventually be designated 2011 MF). With only 45 minutes left before twilight would get so bright that imaging would have to be abandoned, I decided to stop what I was doing and try for one of the LINEAR discoveries.

The two new objects were posted on the NEOCP with the temporary designations assigned to them by the LINEAR team, BZ52584 and BZ52587.

BZ52584 was in reasonably dark sky, about 4 degrees north of M13, the Great Globular star Cluster in Hercules while BZ52587 was much further east, about 3 degrees west of M31, the Andromeda galaxy and already in the glow of the approaching dawn. As BZ52584 was moving twice as fast as BZ52587 and better placed I decided it would be more useful and more likely to succeed to try and confirm it in the short time left before dawn. (BZ52587 would turn out to be a comet and be designated C/2011 M1 LINEAR a couple of days later).

However, the MPC prediction for BZ52584 was a bit odd - LINEAR had only observed it for 60 minutes some 18 hours earlier and normally the MPC would provide both a predicted position for the new object as well as an uncertainty map showing the likely area of sky the new object might be found in. However, this time only the predicted position was given, no uncertainty map. I took a set of images centered on the predicted position between 01:20 - 01:40 UT but when examined, there was no trace of the new object. With only about 20 minutes of usable sky left I started to hunt for BZ52584. With time only to take one or two more fields of view I chose to start with the field of view immediately to the east of the MPC predicted position.

As there was so little time left, the images were examined as soon as they were downloaded from the camera and after 7 minutes collecting 13 images it looked like there was a probable candidate, moving with the right motion, over 1/4 degree from the original prediction and just 17 pixels from the bottom of the images!

Two fields taken during the hunt for BZ52584. White denotes the first, centered on predicted position, yellow indicates the field where the object was found, very close to the bottom of the frame

One or two of the images had been spoiled by clouds that had started to thicken up and in a desperate attempt to positively confirm the new discovery before being clouded out I repositioned the telescope to centre the suspected object in the field of view and get some more images. The clouds continued to thicken and only 5 of 23 images taken after repositioning were at all usable, but fortunately they did show the new object in the expected place.

All of the good images were then measured and positions sent off to the MPC at 02:05 UT.

Animation of 2 sets of 5 x 20 second stacked exposures, showing motion of 2011 MD
01:41-01:45 UT 23 June 2011

The three positions I had just measured and the four provided by LINEAR were then put into FindOrb to work out an orbit and to provide an early view of where the new object was going to be in the next few days. It was immediately apparent that it was headed for a very close approach to Earth in 4 or 5 days time and so, to alert other observers and the MPC, I posted on the MPC's NEOCP blog at 02:16 UT:

"J95: BZ52584 probable v. close approach on June 27.2 UT"

"FindOrb gives ~23,000Km on June 27.2 UT (leaving out 1 of 704 positions). Worth
some more follow-up."

With further positions measured from other observatories in the following hours, the new object was announced by the MPC as 2011 MD later on June 23 and the close approach turned out to be somewhat closer than that first prediction, at 18,700 km from the Earth's centre on June 27.7 UT, or just under 1 Earth diameter from the Earth's surface.

2011 April notes: 2011 GP59 and NEOCP changes

2011-05-08T18:23:00.003+01:00

April continued the good spell of weather that set in during March and ended up being the warmest April since records began for the British Isles. Plenty of Near-Earth asteroids were picked up by the surveys but probably the most interesting object was 2011 GP59 which was discovered by the amateur run La Sagra survey in southern Spain just before midnight on April 8th. It was described as mag +17 by the discoverers and was heavily observed from Europe in the next few hours, with 45 positions being reported by the time I sent my first position in, just 2 hours after discovery. It was immediately obvious that it was varying greatly in brightness in the space of just a few minutes and it could be seen to brighten up and then fade completely from view in real-time as sequential images were captured and displayed on the pc. Also evident early on that first night was that it would brighten over the coming days and make a close approach about a week later. It passed Earth at 1.4 Lunar Distances on the evening of April 15 but at a southerly declination and running into evening twilight so difficult to observe from the UK. Nick James posted a very good animation on YouTube showing the rapid brightness changes from the night of April 11th.

I last observed it in the early hours of April 12th when it was 16th mag and still moving relatively slowly at 9"/min., obtaining 376 images over a three hour period to try and determine a lightcurve. The initial reduction of the data showed a dramatic curve with a 2 mag amplitude and a period of just over 7 minutes. However, there was quite a noticeable scatter in the brighter segments of the curve, just where the errors would normally be expected to be at their smallest.

Initial lightcurve reduction, showing large scatter at the brightest part of the curve, where scatter would normally expected to be least

So Canopus was used to try and determine whether the object was tumbling and if a secondary period was contributing to the scatter of the main curve. Canopus has functionality to determine an initial lightcurve and can then subtract that modelled variation from the original data points. The adjusted data points can then be used to try and solve for a secondary period. If a secondary period is apparent, then this can in turn be subtracted from the original data points and a fresh determination of the primary period made. A few of those iterations for 2011 GP59 resulted in the two lightcurves shown here, the main one with a 7.352 +/- 0.002 minute period and 1.8 mag amplitude, while the secondary period was found to be 10.25 +/- 0.02 minutes with an amplitude of approximately 0.4 magnitudes. There is a great deal of scatter throughout the secondary lightcurve and it is best viewed from several feet away(!) when the sinusoidal lightcurve becomes much more apparent. The overall noise is mainly due to the secondary period being superimposed on the large 1.8 magnitude variation of the primary period and therefore both the maximum and minimum of the secondary curve have data points contributed from the faintest parts (as well as the brightest parts) of the overall variation, so low signal/noise ratio measures, with large scatter are unfortunately present throughout the secondary curve.

Primary lightcurve with secondary subtracted

Secondary lightcurve with primary subtracted

Using measurements obtained by the Lowell Observatory from the previous night, tumbling asteroid expert Dr Petr Pravec reported similar results in the Minor Planet Mailing list here http://tech.groups.yahoo.com/group/mpml/message/25234 with periods of 7.3501 +/- 0.0004 minutes and 10.258 +/- 0.003 minutes.

Users of the NEO Confirmation web page will have noticed during late April that the number of objects on the page has exploded from what in previous months had been at most around 30 objects at any one time to much higher numbers, for a while in the first few days of May there were over 160 objects listed. The surveys are not necessarily picking up any more NEOs than they had done a few days earlier, rather the Minor Planet Center (MPC) has changed the threshold "NEO probability" that a newly discovered object has to score to get onto the page. Following a workshop in March that included representatives from all the NASA funded surveys, JPL and the MPC, the attendees overwhelmingly voted for more objects to appear on the page, so objects that only have a small chance of actually being a NEO (such as objects with Mars crossing orbits, Hungarias, Phocaeas etc.) are now appearing on the NEOCP along with more definite NEOs.

As an observer, the sheer number of objects on the page makes target choice very difficult and to help, the MPC are making some modifications. Initially they have started displaying the NEO probability as a percentage against each object, so the observer can choose objects with high scores, say 50%+ if they want to have a good chance of observing a new NEO. In beta test now and hopefully soon to be introduced fully is a means of filtering the page by magnitude, declination and NEO probability which should make planning an observing session much easier.

2011 March notes: 4 close approach NEOs

2011-04-10T23:30:00.004+01:00

Fortunately March broke the 4-month run of very poor observing conditions at Great Shefford, with 16 usable nights and additionally plenty of Near-Earth objects to observe. March and Oct/Nov are the months that the surveys are generally most successful at discovering very close-approaching minor planets and this month they again had a bumper crop.

2011 EY11 discovered on March 5th with the Mt. Bigelow Schmidt by the Catalina Sky Survey team made a very close pass to just 0.34 Lunar distances (LD) from Earth at 03:36 UT on March 7th. It was picked up from Great Shefford just before 8pm on March 6th when it was already 16th mag and moving at 170"/min. It had come inside the orbit of the Moon about an hour before, but when last recorded, at 01:55 UT on March 7th was 0.38 LD away and travelling at over 800"/min. Heading almost due South its declination decreased from +16° to -25° in the 6 hours it was under observation and was likely to be only about 6 meters in diameter. It showed large and very rapid variations in brightness of 1 mag or more, but a lightcuve has not yet been reduced.

Another discovery from March 5th with the Mt. Bigelow telescope was 2011 EC12, which was to make an approach to 3.3 LD during the early evening of March 8th. It was observed at mag +16.7 and moving at 100"/min on the night before closest approach but when observed at the point of closest approach on March 8th was up to 0.7 mags fainter due to the rapidly increasing phase angle and it had accelerated to 150"/min too, both factors making it a more challenging object that second night.

2011 EU20 was first picked up by the Mt. Lemmon 1.5-m telescope of the Catalina Sky Survey on March 8th, 3 days before making a pass to within 1.62 LD of Earth. Observed on the night of March 9th at mag +17.2 and again the next night at mag +16.1. When last detected at 03:36 UT on March 11, 7 hours before closest approach it was at 1.7 LD and moving at 160"/min. Again, relatively small, with an estimated diameter of about 11 meters.

2011 EW74 discovered on March 15 from Mt. Bigelow was a larger object with an estimated diameter of 65 meters and made an approach to 10 LD on March 21. Even though more distant than the other objects mentioned, because of its larger size it would still reach mag +16.1 for a few days either side of closest approach. Unfortunately this coincided with the full Moon and for the three days when 2011 EW74 was at its brightest it was always less than 40° from the Moon, reducing the signal/noise ratio of the images and making photometry more difficult. No obvious brightness variations were noted but a full reduction of the images obtained has yet to be completed.

Visit to the Catalina Sky Survey

2011-02-10T02:06:00.003Z

During the first week of February my job took me to Phoenix, AZ and before flying home, I took the opportunity to visit the Catalina Sky Survey (CSS) team in Tucson. I met up with Principal Investigator Ed Beshore and co-P.I. Steve Larson at the Lunar and Planetary Laboratory within the University of Arizona campus for lunch and we were joined soon after by Richard Kowalski and Rik Hill from the CSS and by Carl Hergenrother from the Minor Planet Center (MPC), also based in Tucson.

Later in the afternoon Ed drove me up the winding road to Mt. Lemmon, a 1.5 hour journey, initially crossing the Catalina foothills covered with magnificent Saguaro Cacti. Half way up the mountain, stunning views unfolded across Tucson, to Kitt Peak 55 miles to the southwest and to Mt. Hopkins with the MMT 50 miles south, not surprising the area is dubbed "Optical Valley". Some miles before reaching our destination we passed the snow line and saw the devastation caused by the forest fires that came close to destroying the CSS observatories back in the summer of 2003. Once we arrived at the summit of Mt. Lemmon (9200ft above sea level), the Large Binocular Telescope on the summit of Mt. Graham 50 miles to the northwest was plainly visible, with the lengthening shadow of Mt. Lemmon pointing almost directly at it.

The shadow of Mt. Lemmon pointing almost directly at the Large Binocular Telescope on Mt. Graham 50 miles away (top right in insert)

As the Sun was setting, Ed opened up the dome of the 1.5-m reflector (observatory code G96) and initialised the equipment before the start of the nights NEO surveying. The 4K x 4K CCD is normally operated at -100C but that temperature has recently been difficult to get down to, an air dryer unit used to extract water from the cooling system suspected of being full of water and needing replacing soon.

Ed Beshore opens up the lower shutter of the Mt. Lemmon 1.5-m telescope

The observer for the night, Alex Gibbs arrived and continued preparing the telescope, running through focussing sequences and also choosing fields in the early evening sky ready for the survey work to start. Two computer flat screen monitors arranged side-by-side displayed the sky divided up into the fixed 1.2 x 1.2 field centres that are used night after night for all the survey work. Settings allowed the areas of sky that CSS and the other surveys such as LINEAR and Spacewatch had covered in recent nights to be colour-coded so that fresh unsurveyed sky could be targeted that evening.

Field centres for the 1.5-m telescope, colour-coded showing where NEO surveying had been done in recent nights by other surveys

Alex clicked on sets of 12 adjacent fields with the mouse, each set of 12 fields would be automatically imaged one after another, going around the set a total of four times. All the images would then be fed into the processing pipeline for automatic moving object detection. Lines on the computer screen marking out 60 elongation from the Sun indicate the westernmost boundary and surveying then proceeds to the east as the night progresses, with the observer manually choosing the areas of sky to be targeted. Earlier in the week Pan-STARRS had been given a complete night dedicated to NEO detection, resulting in 27 Pan-STARRS objects being on the NEO Confirmation Page, most very faint at mag. 22-23 and out of the reach of amateurs. Alex selected some of the sets of survey fields to cover the uncertainty areas where some of the Pan-STARRS objects were located to try and help recover them. As astronomical twilight ended the exposures started and soon the first set of 12 x 4 images had been processed and was ready for examination.

Alex Gibbs selecting fields at the start of a night of NEO surveying by the 1.5-m Mt. Lemmon telescope

The CSS software detects objects that have consistent movement on all four frames of each field, down to a signal-to-noise threshold of about 1.2 (i.e. deep into the random noise in the images) and then matches those detections against the latest orbits in the MPC's MPCORB Minor Planet database. Each set of four images is then blinked, with known objects marked in green. All the remaining detections are then visually checked by the observer and those that look convincing are manually selected, the rest discarded. A score is then determined for each new object depending on its rate and direction of motion, together with where it is located in the sky to indicate its chance of being a NEO. Astrometry is measured for all the objects and sent off to the MPC, any objects that look like they are particularly interesting have further exposures scheduled for later in the night to help with the follow-up effort.

With the 1.5-m telescope in full operation, Ed and I left to drive the 7 miles down to Mt. Bigalow where the CSS 0.68-m Schmidt is located (observatory code 703), 1000ft below the Mt. Lemmon telescope. That night Andrea Boattini was the observer (he was the only member of the CSS team I had met before, at the MACE meeting in Mallorca in 2003) and as we arrived he was busy blinking a set of images with 100+ moving objects, expertly selecting or rejecting the automatic detections at a remarkably fast rate!

Andrea Boattini blinking newly detected moving objects at the controls of the CSS 0.68-m Schmidt

Ed and Andrea discussed recent adjustments to their procedures for the Schmidt, increasing exposure length to 60 seconds to try and detect fainter objects, at the expense of reducing the amount of sky they would be able to cover per night. We left Andrea blinking the latest set of images processed through the pipeline and drove back down the mountain with both telescopes continuing to work flat out. What a night...

2010 XM56

2011-01-06T01:34:00.004Z

December and November were very disappointing months, the smallest amount of clear skies here for seven years, indeed my counts of nights used (169) and hours spent imaging (702) for the year were also the lowest since 2003. I recall writing this time last year how 2009 had produced the best observing figures since my observatory was commissioned in May 2002... I should have kept my mouth shut!

On one of the rare decent nights in the month, I followed Apollo 2010 XM56 for 5.9 hours on December 16th. It had been discovered a week earlier by LINEAR and with an estimated diameter of only about 30 meters it was predicted to reach mag. +15 as it passed by Earth at slightly less than 2 Lunar distances. During the night its apparent speed accelerated from about 160"/min up to 250"/min and only stayed in the same field of view for 4 minutes at the start of the night and 3 minutes by the end. It was obviously varying substantially in brightness with a period of about 2 hours. I stacked all the usable images from each of the separate fields of view taken during the night and ended up with 96 photometric measures. The raw lightcurve shows a plot of relative magnitude against fractional Julian Day (0.5 = December 17.0 UT) and shows the amplitude of the brightness variation increasing from an already substantial 2.5 magnitudes at the start to 4.4 magnitudes by the end of the night! By the end, the object was changing from being very well recorded on individual 2 second exposures at maximum, then fading within 1/2 an hour to being completely invisible on individual images at the deep minimum, though the multiple image stacks made at minimum still recorded it well. Some of the increase in amplitude will be due to the rapidly increasing phase angle (47° increasing to 65°) as shadows lengthened on the surface of the object although there may also be some variation due to tumbling. The period was determined to be 2.35 +/- 0.02 h.

Raw lightcurve of 2010 XM56 from 2010 Dec 16/17th

Chang'e 2 booster

2010-12-07T03:05:00.003Z

Here is a lightcurve derived for 2010-050B which appears to be the booster that helped launch the Chinese Chang'e lunar mission. It was on the NEOCP for a while and looks like it will be visible for a while at least as a NEO-like distant artificial satellite. The lightcurve is from 246 exposures taken on 25 Nov. which shows a 26.89 sec rotation period with an amplitude of about 3.0 mags and I interpret it as representing a generally regular, elongated object, but as the "dark" ends point towards us, one end produces a bright (2+ mag) flash, lasting just 2.6 seconds centered at about phase=0.56 and the other end produces a much fainter flash (<1 mag.) for about the same duration at phase=0.06.

Lightcurve of 2010-050B (the booster for the Chinese Chang'e mission)

2010 September notes: 2010 RX30, 2010 RF12 and the pair 2010 RX3 and RY3

2010-10-05T22:31:00.004+01:00

Good weather from Aug. 29 to Sept. 17 resulted in a run of 17 out of 20 nights usable for observing, but unfortunately the last half of the month could only manage three. There was plenty of NEO activity in early September, with a number of close approaches:

2010 QG2 had been discovered on the last day of August by LINEAR and was followed on the nights of Sept. 1 & 2 at mag +17.0 as it passed by at 5 Lunar Distances (LD).

The Catalina Survey Mt. Lemmon station discovered two small asteroids within about half an hour of each other on Sept. 5th and both came closer than the Moon three days later. 2010 RX30 is probably about 11 meters in diameter and passed at 0.64 LD on Sept. 8th at 09:51UT, closely followed by 2010 RF12 (~7 meters dia.) which came as close as 0.2 LD or just 6 Earth diameters at 21:12 UT the same day.
2010 RX30 was imaged on the nights of 5th, 6th and 7th Sept. and on the last night was 16th mag. and moving at 160"/min, at a distance of 1.2 LD. It was last seen by Richard Miles using the 2-m Faulkes Telescope North just half an hour before closest approach by which time it was 14-15th mag. and moving at 520"/min!
2010 RF12 was well observed by many people in the run up to its fly-by and again was tracked from Great Shefford on the nights of 5th, 6th and 7th September. When last seen, before clouds moved in it was also 16th mag. but moving slower than 2010 RX30 at 37"/min and at a distance of 1.1 LD. David Herald in Australia was the last to report positions for it, 11 hours before closest approach and by then it was 14th mag., moving at 168"/min at a range of 0.5 LD.

Just before month end, 2010 SK13 passed by at 0.7 LD and was observed on the night of 29th Sept. at mag +17 when it was 2.4 LD away. It was closest at 15:58UT on the 30th but was last reported 7 hours earlier from the Magdalena Ridge Observatory in New Mexico, before it had crossed within the orbit of the Moon.

Probably the most unusual discovery was made on Sept. 2nd, again from Mt. Lemmon. Two objects were put on the NEO confirmation page travelling at almost the same speed and in the same direction, one moving at 10.6"/min in p.a. 77.5°, the other at 10.8"/min in p.a. 78.5°. Added to that, they were of similar brightness and only 1.5° apart in the sky. They were designated 2010 RX3 and 2010 RY3 the day after discovery but unfortunately they were already mag. +21.2 and +21.4 and within a day or so of their brightest for this apparition. I managed to record both on two nights, but they were always very difficult objects and both were lost after only 7 days. The orbits for both are necessarily still somewhat uncertain after such a short arc but the elements are very similar and indicate that the two objects were probably gravitationally bound in the recent past. The JPL Small-Body Database Browser at http://ssd.jpl.nasa.gov/sbdb.cgi gives the following orbits for the two objects:

2010 RX3	2010 RY3
T = 2010 Sep.29.70 ±0.04 d	T = 2010 Oct.01.85 ±0.04 d
q = 1.00365 ±0.00009 AU	q = 0.99181 ±0.00004 AU
Q = 4.26 ±0.05 AU	Q = 4.29 ±0.05 AU
e = 0.619 ±0.005	e = 0.624 ±0.005
a = 2.63 ±0.03 AU	a = 2.64 ±0.03 AU
Peri = 202.26 ±0.02°)	Peri = 206.06 ±0.02°)
Node = 172.69 ±0.03°)2000	Node = 171.99 ±0.02°)2000
Incl = 3.89 ±0.02°)	Incl = 4.44 ±0.02°)
H = 25.06	H = 25.07

2010 August notes: (105) Artemis occultation, NEO discoveries and recoveries

2010-09-10T00:47:00.003+01:00

The amount of activity on the Minor Planet Center's NEO Confirmation Page (NEOCP) was as expected, quite low during August, with the telescopes of the Catalina Sky Survey being out of action during the monsoon season in the South-West USA. However, LINEAR picked up a number of new objects, as did the WISE Infrared satellite above the atmosphere.

A LINEAR discovery designated 2010 PJ9 passed by at just under 3 Lunar Distances (LD) late on August 9th but weather only permitted catching it from Great Shefford on the morning of the 8th when it was at 6 LD and 16th mag, moving at 30"/min.

2010 PR66 was another LINEAR discovery made on August 15th and confirmed from Great Shefford later the same day. It was about 18th mag at that time but had reached 14th mag 3 weeks before discovery as it made a 10 LD approach in the evening sky that had gone completely unobserved. LINEAR's discovery was impressive, deep in the rich star fields midway between Sagitta and Delphinus, their search algorithms must be very good. Finding moving objects in rich star fields is something that LINEAR still seems to do better than the other surveys. For me, even knowing where to look, it took some time and many exposures to pick it out from the background stars, just to get a few position measurements.

Another stellar occultation was recorded, this time by (105) Artemis on the evening of August 18th (see details including the drift-scan image here). I recorded an 8 second event and Roger Stapleton in St. Andrews also recorded a positive event. The timings from these, together with three other observers in Europe allowed the 123 x 87km oval shape of the asteroid to be mapped out and the result can be seen on the European Asteroidal Occultation Results page for 2010. Click on the chords link to see the result and the link to the observers list showing all those contributing measurements to the the diagram.
I took some images of (105) Artemis before the occultation and measured astrometry from them, sending the positions of (105) Artemis to the Minor Planet Center. It was only later that I recalled that Artemis had been a target of mine 33 years earlier, from my previous location of Cheam (station 499) where I had submitted a single position from 1977 May 22, taken with a 300mm focal length telephoto lens with a 2x converter on Tri-X film, reduced by hand with the SAO Star Catalogue. That result still sits in the Minor Planet Center database and is now joined by my three (new technology) positions from 18 August 2010!

During a quiet NEOCP period towards the end of the month I set about trying to recover some NEOs that had only been seen at one opposition and were predicted to be having reasonably favourable apparitions now. I managed to locate four objects (2006 FE, 2007 VC138, 2008 TC4 and 2009 PY) on the night of August 30th and the weather held up enough for me to get confirming positions the next evening. I was very lucky with 2006 FE to pick it up by chance in a very rich star field in northwest Aquila in the first set of exposures taken, travelling across a little 1 arcmin void amongst the milky way background. The most challenging recovery though was 2009 PY, 20th magnitude and half a degree from prediction, requiring a number of my 18'x18' fields of view to be searched before finding the tell-tale motion of the faint NEO.

2010 July notes

2010-08-08T21:25:00.001+01:00

July was very disappointing with only 21 hours observing, spread over 10 rather poor nights, my worst monthly figures since June 2007 and my worst July since the observatory started operating in May 2002. The best of the skies were at the beginning of the month.

Early on 4th July the 1.5-m scope on Mt. Lemmon picked up Apollo 2010 NG, over 15 Lunar distances (LD) from Earth, but due to pass at just under 6 LD on July 13. Although probably only about 30 meters in diameter it was predicted to reach mag. 17 as it plunged far south in the days leading up to its close approach. I caught it on the nights of July 4, 6 and 9 before it went out of view, the last night it was moving rapidly south, at a declination of -25 and only 10 degrees above the horizon.

One other object which was followed for three consecutive nights in early July was 2010 NB, a 19th mag LINEAR discovery from July 1. By July 3.0 when I first observed it, it was moving north, at a high northern declination and fading fast - it had evaded discovery during the last week of June when it was at its closest and was already a magnitude fainter when LINEAR picked it up. It was last detected by the Astronomical Research Observatory, Westfield, USA on July 6.2 at magnitude +21.4.

2010 May notes: MACE 2010, (130) Elektra occultation and 2010 KQ

2010-06-08T01:31:00.010+01:00

After a four year gap since the last "Meeting on Asteroids and Comets in Europe" (MACE) in Vienna in 2006, the 5th MACE took place in Visnjan/Tican, Croatia during 21-23 May (http://www.minorplanets.org/MACE2010/). Richard Miles and I attended from the UK and in all about 50 amateur and professional astronomers from all over Europe attended, together with Steve Chesley/JPL from the USA. Richard and I had the pleasure of meeting Jan Vales (P/2010 H2), discussing at length with him and others Richard's ideas on possible mechanisms that may have caused the dramatic outburst that led to Jan's discovery. The meeting also boasted comet discoverers Michel Ory (P/2008 Q2) and Eric Elst (133P/Elst-Pizarro), Korado Korlevic (183P/Korlevic-Juric and 203P/Korlevic) and of course the meeting organizer Reiner Stoss, co-founder of the La Sagra Sky Survey team that is credited with comets P/2009 QG31, P/2009 T2 and P/2009 WJ50.

Following on from the (130) Elektra result (TA 551,299), another occultation was successfully captured from Great Shefford, this time of the mag +10.5 star TYC 5573-00543-1 by (80) Sappho on June 4. The drift-scan image shows the starlight being blocked out by the minor planet for 5.5 seconds and revealing the minor planet shining faintly at mag. +11.8. John Broughton's SCANALYZER software was used to reduce the time of disappearance and reappearance (see full details here). At least one other UK observer, Tim Haymes in Maidenhead, Berkshire is also known to have succeeded in obtaining a positive result and other results are expected from France and Italy, which may lead to a determination of the asteroid's shape when all the results are in.

As well as a few very close approaches by newly discovered minor planets (the closest being 2010 JV39 to 0.65 Lunar Distances (LD) on May 26 and 2010 JL88 to 1 LD on May 17) there was also the discovery of unusual object 2010 KQ, originally added to the Minor Planet Center's NEO Confirmation page (NEOCP) on May 16 and observed from Great Shefford on the evening of May 17. Soon after my positions were sent in to the Minor Planet Center, Associate Director Gareth Williams removed it from the NEOCP with a note "was not a minor planet", adding it instead to his "Distant Artificial Satellites Observation Page" at http://www.minorplanetcenter.org/iau/SpaceJunk/SpaceJunk.html and indicated to me that further observations would still be useful. I got another set of measures the next night and sent them in to the MPC as Artificial Satellite positions. The next day all the positions obtained from discovery to May 18 were published in MPEC 2010-K15, announcing the object as minor planet 2010 KQ! It would approach the Earth to within 1.28 LD on May 21 and then gradually drift away, in an orbit quite similar to the Earth's (q=0.997 AU, P=396 days, e=0.055).
In the next week, spectral measurements were obtained by Richard Miles using the 2.0 Faulkes Telescope North and S.J. Bus using the NASA IRTF telescope, both on Hawaii and both observers determined independently that the spectrum of 2010 KQ does not match any known asteroid type, but is very similar to space weathered titanium dioxide paint and conclude that 2010 KQ is in fact very likely to be artificial. With further positional observations made in June it appears that the object made a very close approach to Earth in 1975, but it has not yet been possible to definitively match it to a spacecraft launch near that time.

2010 March notes: WISE and Pan-STARRS

2010-04-02T19:27:00.002+01:00

Generally poor observing conditions throughout March hampered observing but a number of new NEOs were followed, after they had been posted on the Minor Planet Center's NEO confirmation page (NEOCP), which is now at this new address:http://www.minorplanetcenter.org/iau/NEO/ToConfirm.html

Although the majority of new objects in March were discovered as usual by the Catalina Sky Survey/Mt. Lemmon telescopes, the WISE Infrared Space Telescope has started to make a significant contribution. About 1 in 5 of the objects added to the NEOCP in February and March were WISE discoveries, however, these are likely to be "extra" objects. WISE is in a polar orbit and scans a great circle aligned 90 degrees from the Sun and so most if not all of the WISE discoveries are unlikely to have been found at that time by the other NASA funded surveys that tend to cover the opposition area of the sky, though some may eventually have been picked up by the ground based surveys as the objects tracked across the sky.

WISE uses a 16" mirror to observe in four bands in the infrared and converting the measured IR brightness into likely visual band magnitudes to be included on the NEOCP for Earthbound observers is tricky, some objects being relatively bright in the IR and others fainter. Many of the WISE discoveries are being listed with V magnitudes of 22-23 but some are brighter than these estimates would indicate and potentially in reach of amateurs.

Going after a WISE discovery with amateur equipment involves taking a large number of exposures and having to be resigned to the fact that there is a good chance that the effort will be for nothing if the object is too faint to be detected. However, WISE's IR eye is very good at picking up comets just as IRAS was 27 years ago. So if a WISE object is bright enough to be picked up it is well worth checking the images for signs of cometary activity. Three out of five WISE objects detected in March from Great Shefford turned out to be comets (P/2010 D2, C/2010 D4 and C/2010 E3).

The first Pan-STARRS 1.8-m telescope on Hawaii with its 1.4 gigapixel camera has also started submitting many hundreds of positions of minor planets to the Minor Planet Center this year and it can't be long before this gives all the other surveys some keen competition too.

2010 January notes: 2010 AL30, 2010 AF40, 2010 BC, 2010 BU2 and 2010 BG5

2010-02-05T00:48:00.015Z

A few relatively bright, newly discovered Near Earth Asteroids were followed during the month but the most newsworthy object 2010 AL30 passed just 0.33 Lunar Distances (LD) from Earth on 13th Jan. with the UK unfortunately shrouded in cloud. It was well observed from many other locations around the world and was last reported from Reedy Creek Observatory in Australia at 11:00UT on the 13th, less than 2 hours before closest approach and moving at 840"/min!

Less dramatic, 2010 AF40 had been discovered from Mt Lemmon on 12th Jan. and was followed from Great Shefford on the 17th and 19th. On the last date it was 16th mag., moving at about 40"/min and about 5 LD from Earth. It was last reported later on the 19th from the Sormano Observatory in Italy, going unobserved when it passed Earth at 2.3 LD about 35 hours later.

A Catalina discovery 2010 BC was followed on 16 and 17th Jan. at 17th mag. but it approached to within 8 LD by 24 Jan, maintaining 15th mag. for 4 nights, unfortunately during another cloudy period in the south of the UK.

More luck was had with the LINEAR discovery 2010 BU2, observed on three nights at the end of the month when it passed at 6.5 LD, reaching 16th mag. but with interference from the full Moon. Another LINEAR find, 2010 BG5 was moving almost due north at discovery on 25 Jan. and had already reached a dec. of +72°. It passed less than 4° from the North Pole on 28th and I picked it up in the early evening of 29th and 30th Jan, by which time it was moving at 40"/min. heading almost due south towards the northern horizon. It was at 6.6 LD and within a day of closest approach, but with the phase angle 95° and increasing it was fading fast at 19th mag.

2009 December notes: 2009 WZ104, 9U01FF6, 2009 observing statistics

2010-01-08T15:22:00.002Z

December provided a reasonable amount of observing time but the number of NEOs discovered by the surveys was much reduced, 34 new objects compared to the 116 they picked up in November, so NEO follow-up work was quieter than of late.

As well as following objects on the NEO Confirmation page, the opportunity was taken to follow 2009 WZ104 on several nights to try and determine its light curve. This is an Aten discovered on Nov. 25 by the Catalina Sky Survey and was brighter than 17th mag. for the first two weeks in December. However, not enough coverage was obtained to be able to find an unambiguous period, but it is likely to be longer than 6-8 hours.

The unusual artificial satellite 9U01FF6 mentioned last month in TA Vol 46 No 548 p211 (2009) which is in a 30+ day, very elongated orbit, taking it as close to us as 5 Earth diameters and about twice as far as the Moon at apogee, was picked up again on Dec. 27, three days before perigee. It was only 5" from the prediction calculated with FindOrb using positions from the previous two returns and taking into account Solar Radiation Pressure. Unfortunately the weather stopped any further observations but it should be visible next on the night of 6th Feb. 2010 and then in March a relatively long apparition, from the 11th-15th.

2009 overall was an exceptionally good year for observing at Great Shefford, producing the best observing figures since my observatory was commissioned in May 2002. Several statistics follow, with the previous best figures and year in parentheses: The most nights used (202 vs. 183 in 2003), the most hours spent at the telescope (938h vs. 838h in 2005), the largest amount of time the CCD shutter was open (24d 00h vs. 22d 03h in 2007) and far and away the largest number of images taken in a year (148,361 vs. 92,025 in 2007). That last statistic is in part to do with more Minor Planet photometry being done in 2009 than before, with many objects being followed for long periods of time, collecting many images during a night. The total number of images taken since 2002 passed the 1/2 million mark during the year and now stands at 570,575.

2009 generally seems to have beaten my previous records by 8-12% all round. Lets hope 2010 doesn't let us down!

2009 November notes: 2009 VX, 2009 VZ, 2009 WJ6, 2009 WV51 and 9U01FF6

2009-12-06T23:16:00.003Z

Although many nights in November had interruptions from cloud, observing time was logged on 18 nights and there were plenty of Near Earth Objects to be followed that had been discovered during the month by the surveys.

Apollo 2009 VX had been discovered on Nov. 9th by the Catalina Sky Survey (CSS) as a 19th mag. object but had brightened to 17th mag. by the time it was picked up from Great Shefford early on the morning of Nov 12th, moving at 150"/min. It was then at 2.8 Lunar Distances (LD) and would pass at 2.59 LD at 13h UT the same day.

Another relatively bright new discovery was Apollo 2009 VZ and although it didn't get any closer than 15 LD it remained above 17th magnitude for 12 nights, I recorded it at 15th mag. on Nov. 12 & 14th. 2009 VZ was intrinsically about 5 magnitudes brighter than 2009 VX, which translates to 2009 VZ having a diameter about ten-times larger than 2009 VX (approx. 300 meters vs. 30 meters), assuming similar albedos for the two objects.
2009 WJ6 was another CSS discovery from Nov 19th and was followed from Great Shefford later that same day. By then it was already about mag. +17.0, at 2.1 LD and moving at 58"/min. It reached its closest to Earth at 11am UT the next day at 0.46 LD and was reported from the Westfield site of the Astronomical Research Observatory, Illinois three hours before perigee, at a distance of 0.82 LD.

One other close approach Apollo object was 2009 WV51. Discovered at 7am on Nov 23 by the CSS it was due to pass at just 0.39 LD the next day. I picked it up on the evening of Nov 23 at 17th magnitude when it was at a distance of 2.8 LD and moving at 'just' 22"/min. Watching individual images download it was easy to see it rising and falling in brightness by approximately 1 magnitude in just a few minutes, though the lightcurve has yet to be reduced. It was last reported from the Magdalena Ridge Observatory, New Mexico on Nov. 24 at 05:43 UT with the 2.4-m reflector, at a range of about 1.8 LD. It went unobserved from Great Shefford that night at its closest approach due to bad weather, but would have been 14th magnitude and moving at over 1,000"/min in the early evening of Nov. 24.

The probable artificial satellite 9U01FF6 mentioned last month was due back at perigee early on Nov. 28 after being followed for only 44 hours by 7 observatories at the end of October. I started searching for it on the evening of Nov 23 but given a likely positional uncertainty of up to 1°, the waxing Moon only about 30° to the south and the predicted mag. being +21.2 I was not expecting much success. However, it was picked up only 5' from the predicted position and ranging in magnitude from +20.5 up to +18.9, the standard asteroid magnitude formula obviously not providing a good fit for this object! Further positions obtained on three subsequent nights allowed the effect of Solar Radiation Pressure (SRP) to be determined using FindOrb using all the available observations (26 October - 27 November 2009). SRP effectively pushes an object away from the Sun and the smaller the mass and larger the surface area of the object exposed to the Sun, the larger the discrepancy from Newtonian motion may be observed. Without taking into account SRP the RMS residual for 78 positions over the two apparitions is a very unsatisfactory 16", but taking into account SRP this drops to 0.8". The value of SRP (or Area/Mass Ratio) determined was 0.011 m2/kg which is similar to those determined using FindOrb for other distant artificial satellites, e.g.

LCROSS (incl. Centaur) size 14.5m x 4.7m, mass ~3,200kg, SRP = 0.015 m2/kg
IMP8 size 1.4m x 1.6m, mass 371kg, SRP = 0.010 m2/kg
ASTRON (1983-020A) size 6m long, mass 3250kg, SRP = 0.008 m2/kg

and is 10 times larger than the 0.0011 m2/kg value derived for 2006 RH120 (=6R10DB9), the tiny (natural) minor planet that was temporarily trapped in Earth orbit during 2006-2007. All this points to 9U01FF6 being man-made and from a posting on the SeeSat-L (Visual Satellite Observers) mailing list here http://www.satobs.org/seesat/Oct-2009/0176.html it is suggested that 9U01FF6 is very likely to be from a lunar transfer mission of some kind, but the perturbations on the orbit make identification of the specific launch very difficult. It is noted that some of the Agena rockets for the Ranger missions of the 1960s were in very similar orbits.

2009 October notes: 2009 TM8, 2009 UD, 2009 UV18, LCROSS and 9U01FF6

2009-10-31T01:15:00.004Z

Apollo 2009 TM8 made a very close approach to the Earth early on Oct. 17th about 48 hours after discovery by the Catalina Sky Survey. It was followed from Great Shefford from soon after sunset on Oct. 16th when it was moving at an apparent speed of 180"/min, through to 04:20 UT the next morning by which time it had accelerated to 285"/min. It reached its closest to Earth at 03:37 UT at a distance of 0.9 LD. The brightness stayed fairly constant, around mag. +17.5 all night, the decreasing distance from Earth being offset by increasing phase angle but the large increase in apparent speed made it a more difficult target as the night wore on.

Another newly discovered Apollo, 2009 UD passed Earth at 2 LD on Oct. 20 and was observed on the morning of Oct. 17th for 2 hours and again for 3 hours the next morning when it was at about 3 LD and mag +17.0. Over 1,000 images were obtained in those 5 hours and allowed the determination that this ~15 metre diameter object rotates very fast with a period of 83.7 seconds with an amplitude of about 0.7 magnitudes.

2009 UV18 was an interesting LINEAR discovery from Oct. 22, relatively bright at mag. +18 and unusually large for a new discovery, estimated at over 2 km diameter. With a low inclination and the Earth approaching the ascending node of the orbit the size of the orbit was initially rather indeterminate and attempts at trying to identify it with a known minor planet failed, even though it ought to have been relatively bright in earlier apparitions. Then, on Oct. 29, Rob Matson, well known for precovery work with online image databases managed to find it on old NEAT images from Jan 2004, fortunately only 2.5° from the predicted place, even though the uncertainty was estimated at up to 90°.

The orbit of 2009 UV18 is similar to a Jupiter family comet and although it appeared stellar in images taken on Oct.23 and Oct. 26th it is probably worth keeping an eye on as it approaches perihelion this January in the morning sky. The last favourable return appears to have been in May 1993 when it should have reached mag. +16 and before that spring 1976 at mag +17.

The LCROSS mission was followed one final time on the night of Oct 8/9th. The spacecraft was only 6.4° from the gibbous Moon and internal reflections in the telescope made it a difficult target. Unfortunately the sky clouded over before the LCROSS shepherding spacecraft separated from the Centaur at 02:50 UT, the last images obtained that show LCROSS were taken at 01:56 UT but were so light polluted they could not be measured. The image of LCROSS was taken about an hour earlier, before the glare from the Moon became too strong, less than 11 hours before impact with the Moon.

What initially appeared to be a Near Earth Asteroid discovery was reported by the Catalina Sky Survey on Oct 26 and received their temporary designation 9U01FF6. It was 19th magnitude and moving at 10"/min but was already closer to Earth than the Moon. After follow-up from other observatories that same day it was found to be in a very unusual 31.5 day period, highly eccentric geocentric orbit, taking it to within 82,000 km of Earth (0.2 Lunar Distances) at perigee and out to 761,000 km (2.0 LD) at apogee. With an absolute magnitude of +30.9 it would only be 1-2 metres in diameter if it were a natural object, but smaller if artificial (with a higher albedo assumed). Further observations were made from Great Shefford on the evening of Oct. 27th and the last positions reported this perigee came from the OAM Observatory at La Sagra in Spain early on Oct. 28th.
9U01FF6 is fainter than mag. +21 for most of its orbit but will next be at perigee around Nov. 28th and should reach +16th magnitude but moving as fast as 250"-500"/min on the evening of Nov. 27th. Hopefully it will be recovered in the days leasding up to that but observability is probably limited at most to only 2-4 nights each perigee. It is likely to be an unusual artificial satellite but further observations at the end of November are encouraged.

2009 September notes: 2009 SH2, 2009 SN103, 2009 SU104, LCROSS and Herschel

2009-10-11T11:38:00.001+01:00

September was a busy time for NEOs, with the Minor Planet Center's NEO Confirmation Page (NEOCP) listing many newly discovered objects during the month. On Sept. 17th and again on 26th more than 30 new and potentially interesting objects were on the NEOCP page and by the end of the month an extra 106 NEOs had been added to the MPC's database.

Apollo 2009 SH2 was discovered by Gordon Garradd at Siding Spring on Sept. 18th as an 18th mag. object and was due to make a fly-by of Earth within 3 Lunar Distances (LD) by the end of the month. It reached mag +16 when last seen from Great Shefford on Sept. 29th.

Another Apollo 2009 SN103, this one discovered by the Catalina Sky Survey on Sept. 25th was 19th mag., already within 4 LD of Earth and moving at 11"/min. It would reach its closest to Earth (1.2 LD) at about 05h UT on Sept. 28 as it overtook the Earth on its way to perihelion on Oct. 30th. It was observed from Great Shefford 6 hours before closest approach when it had brightened to 16th mag. and had accelerated to a speed of 138"/min. It was also caught the next night in central Gemini, moving slower at 86"/min but with the phase angle increasing very rapidly, it was 18th mag., fading quickly and was a much more difficult target to record.

It is estimated that 2009 SN103 is only about 8 meters in diameter. Another close approach NEO discovered by the Catalina Sky Survey on Sept. 27th and estimated at about 20 meters diameter was 2009 SU104. This Apollo has a very eccentric orbit taking it very close to the orbit of Venus at perihelion, out to 4.2 AU at aphelion. At this apparition it was on its way to perihelion in Nov., crossing the Earth's orbit just after the Earth had passed by. It was observed at its closest at 2.5 LD on Oct 1st when it was mag. 16 and moving east to west at 223"/min in Equuleus.

Several distant artifical satellites were also followed during the month, including LCROSS on Sept. 12th & 16th before it disappeared into southerly declinations until a few days before its impact with the Moon on Oct 9th. The Herschel telescope was also recorded on Sept. 17th at 19th mag. Ephemerides generated from previous astrometry obtained for this object were useless to try and pick it up again as the spacecraft undergoes frequent orbital manoeuvres to keep it near the second Lagrange point (L2). The JPL Horizons ephemeris allowed Herschel to be picked up without problem, moving at 3"/min.

2009 August notes: 9O0DC57, 2009 QC23 and 2009 QY33

2009-09-06T01:43:00.001+01:00

August carried on the very good trend of the first half of 2009, with 18 usable nights providing 96 hours of observing and with plenty of NEO discoveries made by the US based surveys it was a busy month.

On July 30th a fast moving 15th magnitude object found by the Catalina Sky Survey and designated as 9O0DC57 by them was put on the Minor Planet Center's NEO Confirmation page, only to be taken off again the next day with a note "was not a minor planet", normal procedure by the MPC when an artificial satellite is mistakenly picked up as a NEO.
This one though did not match any of the artificial satellites with published orbits. It has a perigee of 18,000Km and an apogee 1/3 the distance to the Moon, making it easily mistaken for a NEO during a close approach.
I followed it over a number of nights during August and on August 2nd managed to determine that it rotates every 5.6 seconds, following it from 00:29 UT into twilight at 03:16 UT. From 00:27 to 01:52 UT it showed a regular 1.5 magnitude variation, but when next picked up at 02:56 UT it was showing a very short flash superimposed on the regular variation, probably less than 1 second long and of about 0.75 magnitudes amplitude. Only about 10 minutes later this flash had increased to about 1.5 magnitudes. The lightcurve is from 495 measurements of 1 second exposures, folded using a period of 5.620 seconds, with the increasing flash marked with curves A and B between phase 0.10 and 0.35. The inset from a 60 second exposure started at 03:21:26 UT shows the object trail 250" long and captures 11 flashes and the secondary maximum can just be made out just to the right of the bright flash.

An 18th mag object moving at 18"/min at discovery and put on the NEO Confirmation page on August 22 turned out to be an very impressive amateur discovery by Noeline Teamo from the Hibiscus Observatory (F84) in Tahiti. Designated 2009 QC23 it was followed at Great Shefford for a week.

Another amateur NEO discovery was made on Aug 27th by the team at the OAM Observatory, La Sagra in Spain, but because it got a low NEO rating by the MPCs automated procedures it never made it onto the NEO Confirmation Page. Team member Reiner Stoss alerted observers that two nights of positions had been obtained and requested further observations via the Minor Planet Mailing List (http://tech.groups.yahoo.com/group/mpml/message/22231). A set of positions obtained just before midnight on Aug 28 from Great Shefford allowed the MPC to announce the new Amor object 2009 QY33 the next day.

2009 July notes: (216523) 2001 HY7, 2001 AA50, 2009 NL and 2009 OF

2009-08-05T02:20:00.001+01:00

With the short UK nights combined with the summer monsoon starting in the South-West of the US hampering the survey operations, there were only a handful of new Near-Earth objects to observe in July, but several objects were followed on a number of nights in an attempt to construct lightcurves for them.

Aten (216523) 2001 HY7 was observed on three nights in early July, but poor weather prevented getting enough coverage to find an unambiguous rotation period before it had faded out of range by mid-month.

Better luck was had with 2001 AA50, observed on 6 nights between July 20 and Aug 2, which showed an amplitude of 2 magnitudes. A rotation period of just under 26 hours is looking most likely, though a few more nights are still needed to be certain.

Apollo 2009 NL was a LINEAR discovery made on July 13th and was predicted to be magnitude 17 through the rest of the month. Photometry was obtained on 11 nights from July 14-Aug 2 and at magnitude 17-18 the scatter of measurements on individual nights was up to +/- 0.5 magnitudes but even so a likely rotation period of 25.2 hours and an amplitude of about 1 magnitude was able to be derived (see preliminary lightcurve).

2009 OF was another Apollo discovered by LINEAR, this time on July 17th and was initially listed by JPL and NEODys as a virtual impactor. It was observed on four nights from July 19-25, finally being taken off the risk registers on July 26th.

2009 June notes: Observing statistics, 2009 KL8, 2009 MU, 2001 FE90

2009-07-05T21:51:00.004+01:00

2009 has provided some exceptional statistics for Great Shefford so far, more usable nights (103) & more hours used (455) in the first 6 months of the year since the observatory was commissioned in 2002, beating the previous best Jan-June (2005) by 10%. Hopefully the last half of the year will be equally good.

June started with the close fly-by of Apollo 2009 KL8, passing Earth at 5 Lunar Distances (LD) on June 2nd. That night it was moving at 60"/min and fading fast, from 19th to 20th mag. during the course of the night. Two nights before, even though about 30% further away it was about 1.5 magnitudes brighter because of its smaller phase angle and I followed it that night for 1h 45 minutes to try and determine its rotation period. That turned out to be just 2 mins 41 seconds, varying by 0.75 magnitudes and it had managed to complete 32 rotations while I was observing it!

Another close approach occurred on June 24 at 16:50 UT when 2009 MU passed at 2.3 LD. The night before it had been well placed throughout the few dark hours available from the UK and was followed at mag. +16, its speed accelerating beyond 100"/min by dawn. Initial indications are that its lightcurve is irregular, suggesting that it may be tumbling, but further analysis needs to be completed.

The Apollo 2001 FE90 was also observed towards the end of the month. Discovered in 2001 when it reached 18th magnitude, this year it was predicted to brighten to mag. +13.3 as it sped from north to south in the evening sky and was scheduled to be a RADAR target at Goldstone and Arecibo at the end of June. I first observed it briefly following a thunderstorm just after midnight on 26th June and in the 22 minutes before it was obscured behind trees it showed a dramatic variation of over two magnitudes in brightness! I observed it on the three following nights and watched the amplitude reduce to 1 magnitude as the phase angle reduced from 79° to 34°.

The lightcurve derived from about 30 minutes of images taken on the evening of 27 June 2009 is shown, including a mosaic of the images from the same sessions, showing the rise and fall in brightness of the Minor Planet as it trailed (from left to right). As can be seen, the observations cover just a couple of minutes less than one full rotation period.

2001 FE90 - light variations on 27 June 2009

2009 April notes: 2009 DP2, 2009 HH36, 2009 HU11

2009-05-06T21:57:00.000+01:00

Along with the monthly crop of new NEO discoveries followed during April, several other interesting objects were also observed:

2009 DP2 was added to the NEO Confirmation page as a slow moving (0.36"/min) 19th mag object on April 3rd, unusual in that it had already been given a provisional designation by the Minor Planet Center (MPC) some 6 weeks earlier (the D of DP2 indicating it had been designated in the fourth half-month of the year). The MPC had matched the discovery observations from Feb 17 & 20th by the amateur run Observatoire Chante-Perdrix (50 miles north of Marseilles) with new observations from two stations of the Catalina Sky Survey on March 27 and 28 and realized the orbit was unusual enough to warrant posting on the NEOCP. With further positions on April 4th and 5th it was found to be a Centaur with a period of 17 years and perihelion distance of 3.8 AU with aphelion out as far as the orbit of Saturn at 9.5 AU though currently it can't get closer to Saturn than about 1.6 AU.

Another even slower moving NEOCP object, 2009 HH36 also ended up being classified as a Centaur, discovered on April 19th with the 0.9-m telescope of the Steward Observatory on Kitt Peak. A nearby faint field star caused me a few problems when I first observed it on the morning of April 20th. With 2009 HH36 moving at only 0.17"/min it would take an hour to move just 10" and so the star was never far away but by the next night it had moved into clear sky and was much more easily seen.

With observations identified back to March 31 and extending to May 5th the orbit is now given with a period of 45 years and perihelion distance of 7 AU. Aphelion at 18.5 AU is at the distance of Uranus, though again it does not get particularly close to Uranus, but can approach Saturn to about 1 AU. It is currently about 9.5 AU from the Sun and due at perihelion in four years time.

In the images taken for 2009 HH36 on April 20th, another unusually slow moving object (0.30"/min) was seen nearby at about mag +20 and a check of the MPC's Minor Planet Checker web page did not reveal any previously known minor planet candidates in the vicinity. The next night, when following up 2009 HH36, this other object was searched for and found close to its extrapolated position.

I sent off the two nights of observations to the Minor Planet Center, hoping to be assigned discovery credit for a possibly unusual new object, only to find out that it had already been given as a discovery (not surprisingly!) to the Steward Observatory discoverers of 2009 HH36 and had been assigned the designation 2009 HU11. It turned out to be a Jupiter Trojan, fortuitously within just a few arc minutes of the even more distant 2009 HH36 at discovery.

2009 March notes: 2009 DD45, 2009 EW, 2009 FH, 2009 DO111, 2009 FD

2009-04-07T02:12:00.002+01:00

March and October are statistically the most likely months for NEOs to be discovered that will make very close passes, within 1 Lunar Distance (LD) of the Earth and this March was no exception.

March got off to a good start with the very close fly-by of NEO 2009 DD45, the picture taken during brief gaps in clouds just after midnight on the 3rd when it was at about 0.9 LD from the Earth. Unusually, it was bright enough to be observed from three days before closest approach (discovery by Rob McNaught at Siding Spring at mag +18.7), reaching mag +10 briefly at its closest when at just 0.18 LD (less than 6 Earth diameters away!), fading to 16th mag by the time I first picked it up, but then still detectable at mag +19 in the rich star fields 10°N of Vega three nights later, somewhat brighter than predicted by the MPC ephemeris.

Even before 2009 DD45 had passed Earth, the next close approach object was queuing up. 2009 EW was discovered by the Catalina Sky Survey on March 2nd and picked up from Great Shefford on March 3.0 and again on March 4.9, before being followed through the night of March 5/6th when it came to within 0.9 LD. It was last detected 30 minutes before closest approach at mag +17, moving at 466"/min, 22° above the northern horizon.

Remarkably, less than two weeks later on March 17th, another NEO, 2009 FH was discovered by Catalina, 28 hours before an encounter that would bring it to within 0.22 LD of Earth. When first picked up at Great Shefford at 19:38 UT on the 17th it was already within 1 LD, mag +15 and moving at the relatively sedate speed of 57"/min. I followed it for 2 hours by which time it was 0.8 LD from Earth and had accelerated to 75"/min. It was last reported at 05:02 UT on 18th March, 7 hours before closest approach, at mag +13 and moving at 250"/min by the Catalina Sky Survey's Mt. Lemmon 1.5-m reflector.

A very preliminary light curve from 220 brightness measurements on March 17th indicates 2009 FH has a rotational period of only 6 minutes 26 seconds, with an amplitude of about 0.3 mags. It made more than 13 full rotations during the 1h 27 minutes the observations span.

There were a number of other objects that made approaches nearly as close as the Moon, notable were 2009 DO111, passing 1.2 LD from Earth early on March 20th, as bright as mag +12 and showing rotational variations of about 1 magnitude by March 19th and also 2009 FD passing at 1.6 LD on March 27, again reaching mag +12. Unusually, this latter object was not discovered by one of the NASA funded surveys but rather by the team operating the La Sagra Observatory in Southern Spain.

2009 February notes: 2009 BL58, 2009 BG81, 2009 DS43

2009-03-08T01:35:00.000Z

Early in February a few fast movers were observed, Apollo 2009 BL58 had been discovered at the end of January by the Catalina Sky Survey. When first observed on 9th Feb it was mag +17.1 and placed 5° SE of Regulus, moving swiftly SE. It was observed two nights later, 45° further on in Hydra at -25° Dec, a degree S of Alpha Corvus and although still mag +17.7, because of its altitude of only 13° was much more difficult to record. It was just a few hours away from its closest to Earth at 4.8 Lunar Distances (LD) and moving at 70"/min.

Apollo 2009 BG81 was a LINEAR discovery from Jan 31st and picked up on the evening of Feb 1st moving at 51"/min, already as close as 4.6 LD but only 19th mag. It came to 4.4 LD on Feb 2nd and was observed by three other observatories but was not reported after that date. With an estimated diameter of 7 metres 2009 BG81 was intrinsically about 4 times smaller than 2009 BL58.

At the end of the month another small Apollo, 2009 DS43 was picked up on 27th Feb in Sextans, first by LINEAR and 97 minutes later by the Catalina Sky Survey (CSS). CSS reported their observations first and were credited with the discovery. It was mag 18 and moving almost due N at 38"/min. I first observed it on the evening of 28th Feb at mag +17.8 by which time it had accelerated to 94"/min and had reached +39° Dec. By then it was at 6.9 LD and would reach its closest at 3am on 1st March at 6.7 LD. By the evening of the 1st it was at a declination of +76° midway between the Pointers and Polaris, had slowed to 81"/min and receded to 7.4 LD and was fading fast, more than 1 mag fainter than the previous night. The Minor Planet Center didn't receive any further reports of it.

2009 January notes: 2009 BB77, 2008 YG30, 2008 YY32, 2009 BE, 2009 BJ2, 2009 BD, EPOXI, NeXT

2009-02-05T02:33:00.012Z

Congratulations to Richard Miles for his first Minor Planet discovery, 2009 BB77 picked up on Jan 30th while he was imaging Comet 17P/Holmes with the Faulkes North telescope!

January provided decent amounts of clear sky at Great Shefford, with 76 hours logged observing. Several NEOs were followed during close approaches, 2008 YG30 was mag +16 and moving at 70"/min on the night of Jan 3rd, 4 Lunar Distances (L.D.) from Earth and due to pass at 3.6 LD the next day. Early on Jan 4th, 2008 YY32 was observed and at 6 LD was already at its closest to Earth, moving at 50"/min and rather fainter at mag +18.2.

After the full moon, on the night of Jan 20th, 2009 BE was seen at mag +17 when it was at 6 LD, but unfortunately cloud prevented it from being observed again, closest approach was on Jan 23rd at 2 LD. The same night another NEO, 2009 BJ2 was imaged but was probably the most challenging object observed in the month. I had followed it the previous two nights but by Jan 20th it was at its closest at 4.7 LD and at its fastest speed of 60"/min. However it had already faded by half a magnitude to mag +19.1 and was very low in the south, in the centre of Canis Major, about 3 degrees SW of M41. The rich Milky Way star-field made identification difficult and the next (cloudy) night was spent discarding many of the 320 images that had been taken when it was masked by stars and then measuring positions from stacks of the remaining images.

Tiny NEO 2009 BD, discovered by the Mt Lemmon 1.5-m reflector of the Catalina Sky Survey on Jan 16th turned out to be quite unusual. It was moving at 10"/min at discovery, but was already only 3 LD from Earth. Over the next 9 days it would gradually drift closer, passing just 1.8 LD from Earth early on Jan 25th and was observed on 5 nights, the last time early on Jan 26th when it was below Polaris, at declination +84°, mag +18.5 and moving at 26"/min. It is probably only about 5 meters in diameter and currently in an orbit very similar to Earth's, with a period of 372 days, an inclination of 1� and a low eccentricity of 0.05. Bill Gray (author of Guide and FindOrb) writes that the available astrometry from Jan 16-26th allows the orbit to be very well determined and shows that it was last in the Earth's vicinity (at a distance of 1.2 LD) around 16 July 1955, with an uncertainty of only about +/- 1 hour! At 01:03 UT on 2nd June 2011 it is due to approach the Earth even closer at a distance of 346,658 Km (= 0.9 LD) with likely uncertainties of just 15 minutes in time and 300 Km in distance. Unfortunately it will then be far south at a declination of -50°, but coming north a few days later when it should be visible once again from northern latitudes.

Two artificial satellites were also observed with a rather unusual connection to each other: On the night of December 30th the EPOXI spacecraft was tracked while at 0.77 LD, at mag +19.2 and moving at 30"/min, midway between Vega and the head of Draco. This was 24 hours after a gravity-assist fly-by of Earth when it had approached to within 50,000Km (= 0.1 LD). EPOXI is the new name for the fly-by spacecraft of the Deep Impact mission that encountered Comet Tempel 1 in 2005 and now on its way to a rendezvous with Comet Hartley 2 in October 2010. The other satellite was the NeXT mission, being the renamed Stardust spacecraft that collected dust samples from Comet Wild 2 in 2004 and has now been re-directed to encounter Comet Tempel 1 in February 2011 to image the crater left by the impactor from Deep Impact! NeXT was seen briefly on the morning of Jan 13th and also followed for 7.5 hours the following night. When last seen it was at 1.1 LD and mag +17, moving at 11"/min, but due to skim just 9,000 Km (= 0.7 Earth diameters!) above the surface of the Earth less than 18 hours later. Unfortunately the close approach night was clouded out.

2008 November notes: 2008 VV4 = 2001 XQ, 2004 XK3

2008-12-06T00:59:00.001Z

With the amount of clear skies in November only amounting to about 40% of that in October, it was a rather disappointing month.

An 18th mag object discovered by the Catalina survey and observed while it was still listed on the NEO Confirmation page on Nov 7th was subsequently given the temporary ID 2008 VV4 and re-observed on Nov 12th by which time JPL was listing it as a "Virtual Impactor" with 17 possible impacts predicted, the first in 2021. While checking for other NEO targets to observe that night I noticed that 2008 VV4 was in the same area of sky and had very similar speed and direction of motion as the Amor object 2001 XQ, as listed on the Minor Planet Center's List of Bright Recovery Opportunities page at http://www.cfa.harvard.edu/iau/NEO/BrightRecovery.html.

2008 VV4 turned out to be the same as the earlier object, 17° from its predicted position and the recovery of 2001 XQ was announced in MPEC 2008-V57. With a period of 6.96 years the circumstances of this apparition were similar to when first discovered in Dec 2001, with the object being at perihelion in early December and moving swiftly south from high northern declinations during November. With the extra 7 years of orbital arc available, JPL was able to calculate that there was no danger of collision with the Earth and it was removed from their risk page at http://neo.jpl.nasa.gov/risk/.

Another object observed while on the NEO Confirmation Page and ending up being a re-discovery of a previously observed object was 2004 XK3. This time it had been picked up by LINEAR as a fast moving 15th mag object and was 14th mag when I observed it only 15 hours later. It was identified within hours by the Minor Planet Center as 2004 XK3 and removed from the NEOCP. With a period of 1.36 years it had done almost exactly three revolutions in the four years since discovery and in fact was only 7° away from the place in the sky where I had observed it four years earlier.

2008 October: Observing statistics, 2008 UL90, 2008 UT95, 2008 TT26, 2008 TC26, 2008 TQ10, 2008 TR10, 2008 UX202

2008-11-06T01:08:00.000Z

After months of disappointing weather throughout the summer at Great Shefford, October proved to be exceptionally good, with the largest number of hours (125h) recorded at the telescope in a single month since I commissioned the observatory in 2002.

The big news early in the month was the brief appearance of 2008 TC3, hours before impacting Earth early on Oct 7th. However, there were plenty of other new objects discovered by the surveys during the month, with over 50 being observed after having been put on the NEO Confirmation Page (NEOCP) by the Minor Planet Center.

One of the more interesting objects was 2008 UL90, a member of the rare Interior Earth Objects, or so called Apohele class, with orbits entirely inside the orbit of the Earth. There are only 14 definite or suspected members of this class to date. This one was at 66 degrees elongation in the morning sky when observed. It should brighten slightly to about mag +19.7 and the elongation increase by just a couple of degrees by mid-November before it slips back into the glare of the Sun during December.

A few fast movers were also followed, 2008 UT95 was last caught moving at 40"/min, just over 4 Lunar Distances (LD) from Earth on the night of Oct 31/Nov 1st, two days before passing Earth at 1.5 LD, but it was not reported from any observatory after Nov 1st. 2008 TT26 was well observed from a number of observatories during October and briefly reached mag +14 around Oct 22/23 when it was recorded moving at about 50"/min, at a distance of about 3.5 LD.

The good weather brought another record for me, a total of 12 new minor planets discovered during the month, with 9 of them found in the field of NEOCP objects. One, 2008 TC26, turned out to be a Hungaria class object, with an orbit inside the main belt, just further out than Mars and was found in the same field of view as two(!) NEOCP objects, 2008 TQ10 and 2008 TR10. The last of the new objects found was 2008 UX202 on 28 Oct and confirmed 3 nights later. This turned out to have a perihelion distance of 1.68 A.U., just outside the aphelion distance of Mars and like 2008 TC26 is in the inner zone of the main belt.

2008 August notes: Observing statistics, 2004 SB56, 2007 RT12, 2001 QL153, 2008 PG1

2008-09-04T01:59:00.000+01:00

The weather was very poor at Great Shefford in July and August. With 25 hours at the telescope, July provided less than half the observing hours logged for that month in any of the last three years. August was officially the cloudiest August in the UK since records began in 1929 and provided only about 50 (generally poor quality) hours, again well below totals from recent years.

However, the night of August 3/4th provided the opportunity to recover three NEOs not seen since their discovery apparitions and a somewhat unusual confirmation of a NEO Confirmation Page (NEOCP) object.

Aten 2004 SB56 had sped northwards after conjunction with the Sun in July and in the 10 days before recovery had brightened 3 magnitudes and increased elongation from 35 to 72°. With an uncertainty area on the sky of 14' it was picked up only 3' from prediction at mag +16.7 and about 6° from the North Pole, a relatively easy recovery.

Apollo 2007 RT12 had an uncertainty of about 1° and at mag +20.0 was a potentially difficult object to recover, just 1° east of Alpha Cep, deep in the Milky Way. Fortunately it was only 8' from prediction and not involved with any field stars during the time it was imaged. With an absolute magnitude of +23.9, equating to an estimated diameter of 30-95 meters, there have only been 10 other NEOs recovered at a second opposition that are smaller than 2007 RT12. Included in this set are the Earth co-orbital companion 2002 AA29 and the tiny 2006 RH120 that was temporarily captured in Earth orbit during 2006 & 2007. My thanks to Sergio Foglia for providing a list of small NEOs seen at more than one apparition.

The third object was 2001 QL153, an Amor that had been observed for about 4 months and had not been seen since January 2002. It too had an uncertainty of about 1° and predicted to be mag +20.5 and could have posed a problem to pick up. It was in a less crowded field than 2007 RT12 and after more than six years since last being observed was recovered only 9' from prediction.

A LINEAR discovery put on the NEOCP on August 3rd turned out to be something of a puzzle. 2008 PG1 was observed from 9-10am UT on August 3 by LINEAR at mag +19, moving at 9"/min from west to east, in the morning sky about 13° north of Mira Ceti. By 2am on August 4th it was predicted to be accelerating and to have an uncertainty area 1.7° long, extending roughly West to East, in the direction of motion. I eventually confirmed it 43' further west than the most westerly point of the uncertainty area (quite unusual for the MPC prediction to be this far out) and moving at about the same speed as when LINEAR discovered it. The orbit appears to be rather indeterminate but it was announced on MPEC 2008-P14 with just the observations from LINEAR and my set of confirmation positions. The orbital eccentricity had been assumed (done sometimes when the orbit is rather indeterminate, to try and help improve the orbit solution). No other observatories had reported positions for the NEO before I got my next chance to observe the area early on August 9th. By then, using FindOrb software from Bill Gray to generate a large number of 'Monte Carlo' orbits to estimate the likely uncertainty area, it looks like it could have been anywhere in a nearly 3° long band. I didn't manage to locate it that morning nor on my next opportunity 4 days later and it has not been reported from anywhere else since. It is now listed as a Virtual Impactor by JPL with 97 potential impacts, the first in only 5 years time, but with such large uncertainties in its orbital elements the chance of collision then is given as just 1 in 200 million!

2008 June notes: 2008 LA, 2008 LG2, 2008 LH2, 2008 LB, 2003 OB4

2008-07-05T23:30:00.003+01:00

After a rather lack-lustre May, June provided the best stats I've logged for that month since my records started in 2002, with 16 at least partially usable nights and 47 hours at the telescope.

This time of year, activity on the NEO Confirmation Page is tailing off as the main NASA survey sites in the southern USA get closer to the summer monsoon season, even so, there were 22 new NEO discoveries announced and 9 of those were observed, with 2008 LA and 2008 LG2 being followed on 5 nights each and still being listed (July 5th) as 'virtual impactors'. Another NEO 2008 LH2 was confirmed soon after LINEAR discovered it, just after its closest approach to 9 Lunar Distances (LD) and followed for a total 7 nights.

2008 LB was the closest and fastest moving NEO seen during the month, a difficult Apollo object, last recorded 16 hours before its closest approach at about 3.8 LD, mag +17.9 and moving at 83"/min through the very crowded star fields just 5° south-east of the Scutum star cloud.

Another object recorded in a rich star field was 2003 OB4, this Amor type NEO had been discovered by NEAT on 23 July 2003 and, with prediscovery images, had been tracked for three months that year but not seen since. I searched for it on several nights in eastern Ophiuchus and found it over 0.5° off-track on 9th June at mag +19, confirming it the next night, with the recovery being announced in MPEC 2008-L43.

2008 May notes: 2008 JL24

2008-06-05T20:44:00.002+01:00

After a promising opening week, May turned out to be yet another disappointing month, with just a handful of (cloud interrupted) nights.

The most interesting object observed during the month was 2008 JL24, a mag +17.5 LINEAR discovery added to the NEO Confirmation Page (NEOCP) just before midnight on 11th May and predicted to be moving at about 25"/min. The sky cleared at Great Shefford a couple of hours later and I started searching for it at 00:25 UT. The uncertainty area indicated by the Minor Planet Center was about 80' wide, much bigger than my 18'x18' field of view. I started imaging at the nominal position, at the western end of the area and while the first set of images was being taken I checked with FindOrb whether by chance any of the astrometric positions submitted by LINEAR had poor residuals, in case I could possibly improve the prediction. All the positions looked good, but the ephemeris generated by FindOrb had the object way off to the east, beyond the furthest eastern extent of the NEOCP uncertainty area.

I decided to start searching from the FindOrb prediction and to work my way back to the western side of the NEOCP area with overlapping fields. I picked up the NEO in the corner of the second field attempted, over 1.5 degrees from the nominal position, but in fact only 10 minutes after I had started observing! I re-centred and obtained some further images and sent off the astrometry to the Minor Planet Center.

Initial uncertainty area for 2008 JL24.
White cross is MPC expected position, orange and red dots indicate MPC expected uncertainty area, yellow boxes are telescope fields originally planned to cover MPC uncertainty area.
4 coloured boxes on left show the search fields taken, with the actual position of 2008 JL24 marked with a red cross. Arrow length indicates the motion of the NEO in 1 hour.
Sky chart and field boxes plotted using SkyMap Pro 9.

When LINEAR discovered 2008 JL24 it was just inside the orbit of the Moon, at 0.94 Lunar Distances (LD) and by the time I confirmed it 18 hours later it had already receded to 1.4 LD. Over the years LINEAR has discovered a number of fast moving objects that were probably closer than the Moon at the time, but never picked up again and in fact 2008 JL24 is the first time that a NEO has been discovered while closer than the Moon and then subsequently confirmed. It was well observed over the next five days before fading out of sight just before the full Moon.

2008 April notes: 2008 GM2, 2008 GF1

2008-05-07T20:41:00.001+01:00

After a good run of more than a week of clear nights in early April, the rest of the month brought rather poor weather, only a couple of nights in the month were were completely cloud free.

Two NEOs (both discovered during April with telescopes of the Catalina Sky Survey) came closer to Earth than the Moon, 2008 GM2 was discovered three days after its close pass, so had already receded to about 2.7 Lunar Distances (L.D.) before being picked up. I recorded it about 14 hours after discovery at about 3.3 L.D. but already it had slowed to a very sedate apparent speed of 6"/min.

The other was 2008 GF1, discovered on April 5th just over two days before closest approach and last caught from Great Shefford just before midnight, late on April 6th when it was moving at 70"/min and at mag +17.6, just over 2 L.D. away, about 12 hours before passing Earth at 0.8 L.D. Unfortunately, it was not picked up again, favourable locations for observing the fly-by being in central Asia, so both these NEOs went unobserved when at their closest.

2008 March notes: 2008 EZ7

2008-04-08T08:42:00.016+01:00

Observing was limited in March, a combination of poor weather with very few nights keeping clear throughout and also the telescope being out of operation for a week, the problems eventually being tracked down to a failing mains transformer (see investigation in progress).

On 7th March (four days before the telescope broke down!) the Apollo 2008 EZ7 was discovered from the Siding Spring Observatory in Australia. From its accelerating motion it was obviously already very close to Earth and it was put on the NEO Confirmation page later that day. With a rapidly expanding uncertainty area where the new fast moving object was predicted to be I was fortunate enough to be able to confirm it later that evening at magnitude +17, at an altitude of less than 13 degrees, shortly before it disappeared into trees.

The next night it was to pass only 0.419 Lunar Distances (100,000 miles) from Earth, closest approach being at 01:21UT on 9th March. The first half of the night was cloudly but with breaks expected later in the morning. I started to try for it through gaps in the clouds at 01:47UT at which time it was moving at over 630"/minute. On the first low resolution shot taken to position the telescope, there it was, very obvious as a strong 30" long streak in the 3 second exposure. However, for the next half an hour the clouds stopped me getting anything other than more positioning shots, but eventually it was recorded in a 30 second gap in the clouds, enough to get eight 1 second exposures off. At that point it was magnitude +13, moving at 623"/minute and only about 102,000 miles from Earth.

The eight (rather noisy) images have been combined here with 2007 EZ7 moving from right to left. The field of view is 18'x18' and there is a 2 second gap between each of the exposures.

A few minutes later, when repositioning the telescope for the next attempt I recorded 2007 EZ7 streaking along as before, but also with another very similar streak in the field of view. This turned out to be artifical satellite 1985-048C=15825U, moving at about 900"/minute and more than four times closer than the NEO. I wonder how many NEOs on very close approaches are assumed to be artificial satellites in CCD images?

2007 EZ7 is to the right and 1985-048C is the slightly longer streak to the left below.

At the time of writing there have only been two other NEOs (with well determined orbits) that have been observed closer to Earth than 2007 EZ7, those being 2004 FH and 2006 DD1, but no doubt, with the pace of NEO discoveries at the moment, it is only a matter of time before another is seen to fly past even closer. Just three weeks later 2008 FP came closer than the Moon and was observed by the Catalina Sky Survey only slightly further out than 2007 EZ7, at a distance of 106,000 miles.

2008 January notes: 2005 BT1, BI10604, 2007 XS16, 2008 AV72 = 2000 JF4 = 2006 PH11

2008-02-04T02:38:00.015Z

January was rather disappointing with fewer hours logged observing than for the same month in any of the previous 5 years.

A highlight was the recovery of the Apollo 2005 BT1, originally discovered by LINEAR on 16 Jan 2005 and followed for 47 days. Predicted to have a favourable approach in Jan 2008, a search was started from Great Shefford on Jan 24th, the expected magnitude given by the Minor Planet Center was +19.1 and the likely uncertainty area given as over 8 degrees long, aligned almost North-South.

I covered the central 4 degrees with my 18'x18' field of view during 24/25 Jan and extended this to the N by another degree on 26 Jan but searching was cut short by clouds. Only 0.5 degrees was added to the S the next night before clouds interrupted again, but finally on 28 Jan, on the first attempted field that night the NEO was finally caught, 2.35 degrees off track to the south. It had taken 814 images taken on the four nights, of 30 separate fields to locate it.

The next night was cloudy again in the UK so I contacted Sergio Foglia (IAU code 147) and Luca Buzzi (code 204) in Italy to see if either of them had good skies to try and get a confirming second night of positions for it. Sergio was not able to observe but Luca managed to get some astrometry before he too was clouded out. With the positions from 2008 Sergio then searched for possible images from the old SkyMorph image archives and managed to locate it faintly on two images from 07 Jan 2002 taken with the Palomar 1.2-m Schmidt. All three sets of positions were sent off to the MPC and within the hour MPEC 2008-B60 was issued formally announcing the recovery.

Another extensive search that didn't end up with such a positive result was also a LINEAR discovery found at 03h UT on 16 Jan and posted on the NEO Confirmation page with temporary designation BI10604 just after midnight on 17 Jan. Although relatively bright at mag +17, by the time I could observe on the evening of 17 Jan the uncertainty area was a 1 deg x 2.5 deg oval. I covered the whole area with multiple images being taken of 31 different fields, but did not find it. By the end of the 4 hour session the area had already expanded by a further 0.5 degrees. It never did get recovered by any observatory and two nights later was removed from the NEOCP...

A good set of luck came my way on 7th Jan while I was following up on one of the main belt discoveries I had made in December (2007 XS16). I found a very faint moving object, about mag +21, that did not match any known object and so measured positions of it. I had hoped to try for it again in the coming nights and send in two nights of astrometry to the Minor Planet Center, but clouds stopped any further attempt for over a week. By 17th Jan I decided to just send in the positions as a one night stand (ONS), expecting that I would not hear any more about it. However, by the next day the MPC had managed to match it up to a ONS from the 1.5-m reflector of the Mt Lemmon Survey obtained 5 days after mine on 12 Jan. It was designated as 2008 AV72 and I was given discovery credit for having the earlier of the two ONS!

With this extra data I now realised that other images taken of 2007 XS16 from the previous month might include 2008 AV72 and on re-examining these managed to find it on images taken 29 Dec and then 19 Dec 2007. After these pre-discovery positions were sent in, the MPC quickly managed to find various other ONS back to May 2000 and even two occasions where the object had been given a designation on the basis of two nights of observations (not enough to determine a proper orbit), these being 2000 JF4 and 2006 PH11. Because 2008 AV72 had a 2 month observed arc in 2007/8 it was retained as the primary designation and with observations at 5 oppositions and an MPC uncertainty code of 1 it is now in a state where it could potentially get numbered - not bad for just sending in the ONS from 07 Jan having lost hope of being able to find it again!

2007 December notes: Observing statistics, 2007 XZ9

2008-01-06T17:44:00.001Z

2007 ended up with some surprising statistics for Great Shefford. Even though we suffered the very bad run of summer weather from May through August I ended up with about 5% more nights used than in 2006, about 5% more time exposing the CCD (22 days 3hours in total) and about 14% more images taken than in the previous year.

The Catalina NEO Survey was snowed out for some of the month, though for the remaining time there were still some fairly busy periods, with several occasions when there were 20, 30 or more newly discovered objects needing follow-up on the NEO Confirmation page. More than 50 new NEOs were eventually added by the surveys to the overall tally by month end, despite the weather.

One consequence of the surveys being out of action for days at a time was a good crop of main belt minor planets available for discovery by amateurs. I picked up 12, my highest monthly total and other amateurs were also very successful too. Most of the NEOs observed here were only picked up for one or two nights, with 2007 XZ9 (an Apollo discovered by LINEAR) being observed the longest, but that only for 6 days.

2007 November notes: 2007 VA85 and 2007 VW266

2007-12-04T23:46:00.000Z

The first half of November was reasonable, with at least some clear sky on 11 nights, but just 3 nights in the last half, including the obligatory crystal clear sky from dusk until dawn on the night of the full moon ...

An interesting object found on Nov 4th by LINEAR was 2007 VA85, 18th magnitude and placed at discovery in the early evening sky between Cygnus and Lyra, passing through the Cygnus star cloud during the next week. It was put on the NEO Confirmation Page and left there for nearly 5 days while the Minor Planet Center waited to see if anyone could detect any cometary features. In the end it was announced as a minor planet but with a very unusual retrograde orbit - four months after perihelion at q = 1.1 AU, with inclination = 132 degrees and period just 8.5 years. I followed it through the rich star fields of Cygnus on 5 nights, trying to catch it in enough empty sky to see whether it displayed any cometary features. Finally on 23 Nov I managed to get a total exposure of 41m 40s at a scale of 1.1"/pixel but could not detect any activity at all.

A week after 2007 VA85 was discovered, the Catalina survey's Mt Lemmon telescope picked up 2007 VW266. This was much fainter at mag. 21 and I just managed to catch it on a single night. By coincidence, it too turned out to have a short period retrograde orbit and was left on the NEO Confirmation Page for 7 days but again, no cometary features were detected by any of the seven observatories contributing astrometry. It has inclination = 108 degrees, q = 3.3 and period = 12.2 years.

In the Minor Planet Center MPCORB database there are only 18 minor planets listed with retrograde orbits and of those, 2007 VA85 and 2007 VW266 have the two shortest periods, with 2007 VA85 also having the smallest perihelion distance of the 18. In comparison, the comet with the shortest period retrograde orbit currently known is P/2006 R1 (Siding Spring) with inclination = 160 degrees, q = 1.7 AU and period = 13.3 years.

2007 October notes: 2007 UN12, 2007 US51 and WMAP

2007-11-07T08:28:00.001Z

October provided 13 usable nights for me, about the same as last year, but with only about half the number of hours spent observing it was a rather disappointing month.

A few interesting objects were observed, 2007 UN12 and 2007 US51 were both discovered by the Catalina Sky Survey soon after passing between Earth and Moon. 2007 UN12 passed less than 6 Earth diameters from us on Oct 17th and was discovered four days later, and 2007 US51 passed about half the distance of the Moon on Oct 30 and was discovered about a day later.

Another object put onto the NEO Confirmation page twice during the month (and on a number of occasions in the past too) was artificial satellite WMAP. Sitting at the L2 Sun-Earth Lagrangian point it appears as a very convincing NEO in close proximity to Earth and with plenty of orbital corrections being required to keep it in position it is impossible to predict accurately where it will be over a period of months. It will probably keep making appearances on the NEOCP as it gets 're-discovered' by the surveys every now and then!

2007 September notes: 2007 RJ1, 2007 SU1 and 2007 RS1

2007-10-02T01:43:00.005+01:00

Plenty of clear nights in September with quite a lot of activity from the surveys on the NEO Confirmation page. Indeed, around September 17th there were 32 objects listed, which may be a record.

Several close approaches were observed during the month, including 2007 RJ1 which was followed for 12 days and ended up at 2.8 Lunar Distances (LD) on Sep 16.1UT moving at 102"/min. 2007 SU1 was seen at 6 LD, moving at 44"/min on Sep 27.0UT.

However, the headline object for me was 2007 RS1 on Sep 4th. This tiny NEO was discovered by Steve Larson using the 1.5-m Mt. Lemmon Catalina Sky Survey telescope just before 6am UT on the 4th. It was unusually faint at mag. +20.4 considering it was already moving at 13"/min. Steve managed to track it for over 3 1/2 hours, by which time it had accelerated to a speed of 19"/min and brightened by half a magnitude.

By the time the sky was getting dark at Great Shefford later that day 2007 RS1 was already closer than 1 LD and moving at 150"/min but had not been reported since the Mt Lemmon observations. The positional uncertainty on the sky was rapidly getting worse and predicted by the Minor Planet Center to be about 3.5 degrees at 20:00 UT (11 times larger than my field of view) and set to double in size within the next 70 minutes. I started trying to cover the uncertainty area, starting at the nominal position, but after taking just a couple of fields got a phone call that I needed to pick my daughter up from Newbury (a 20 mile round trip). All I could do was to set the telescope some distance ahead of the predicted place and let it take images while I was away, hoping that the object might just pass through my 18'x18' field of view. I set the exposure length to 4 seconds which would cause the object to trail if it did pass through, making it more obvious to identify but at the expense of some accuracy in measurement.

Background stars appear as lines of dots as the fast moving asteroid is kept in the centre of the image and itself appears as a small streak due to its own movement during each individual exposure

By the time I returned from Newbury the sky was clouding over for the night but I had amassed a total of 756 images, 564 taken in one long sequence while I was driving. After spending a number of hours searching the images I eventually managed to locate the tell-tale streaks of the NEO speeding through some of the images taken while I was away from the observatory. Remarkably it passed almost centrally through the field of view, taking just four minutes to pass from one side to the other. With the ephemeris corrected I was then able to find a few more images of it entering the field of view at the very end of one of the early runs I took before I left.

The last images that recorded it were taken at 20:39 UT when it was mag +18, moving at 246"/minute and with it 0.55 LD from Earth. It was to pass just 0.19 LD from Earth, or less than 6 Earth diameters away at 01:18 UT on September 5th, but was it was not reported again.

JPL is listing 2007 RS1 with the faintest absolute magnitude of any Minor Planet, with H = 30.98 +/-0.36, the previous record being 2003 SQ222 at H = 29.99 +/-0.70. It is likely that 2007 RS1 is only about 1 or 2 meters in diameter.

2007 August notes: 2007 QA1

2007-09-07T18:24:00.001+01:00

August saw a rash of new main belt objects picked up from Great Shefford and as I write this four have very good, secure orbits, three others are OK with several weeks of observations and one I only managed to record on two nights and so is effectively lost.

2007 QA1 was another new object I picked up on the night of Aug 16 at mag +19.0 which turned out to be interesting - it was heading almost due south (in p.a. 195 deg) though was not moving unusually fast. I could not identify it with any known object on the MPCs Minor Planet Checker web page. I also checked it against the MPCs NEO rating page to see if it had any chance of being a NEO and that came back with a very low rating of 3% (50%+ is required to get an object placed on the NEO Confirmation Page). I held onto the positions to try and get a second night but the next night was cloudy.

Later that day the MPC added it to the NEOCP, having received positions from the Lowell Observatory. Although it did not end up being a NEO (perihelion distance was just greater than the 1.3 AU limit) it was a Mars crosser and having appeared on the NEOCP from Lowell it was effectively lost to me as a discovery - the first observatory reporting even a single night of observations will be granted discovery credit if it appears on the NEOCP, unlike normal Main Belt objects where it is generally the first observatory to report two nights of positions that gets discovery credit.

Lesson learned: Don't rely on the NEO rating page to decide if an object is interesting! In fact it's motion was very unusual, of the 1794 minor planets that were mag +23 or brighter within 5 degrees of 2007 QA1, only one other was moving in a direction with a p.a. less than 209 degrees. Next time(and I hope there is one!) if another potentially interesting object turns up I will submit a single night of positions to the MPC and let them decide whether it is interesting enough to put on the NEOCP...

2007 July notes: Floods, 2007 DT103, 2007 MB4 and recovery of 2001 RV17, 2005 XW77 and 2003 CG11

2007-08-06T21:16:00.001+01:00

The continued bad weather here culminated in flash flooding on 20th July which left us with two rooms under water, but fortunately the observatory stayed dry. Since then the weather has noticably improved with a run of good clear nights in the last week of the month.

During the month three NEOs were recovered at their second apparition - 2001 RV17 at the beginning of the month with 2005 XW77 and 2003 CG11 towards the end, both of those two in collaboration with Luca Buzzi at the Schiaparelli Observatory in Italy.

A couple of moderately fast movers were followed over several nights - 2007 DT103 which was detected at the end of the month by RADAR from Goldstone and found to be a binary, and 2007 MB4 that passed at about 8 Lunar Distances on July 5th.

2007 June notes: 6R10DB9's fourth and final perigee

2007-07-05T00:20:00.001+01:00

As anyone in the UK will already know, the poor weather in May just got worse through June. I suffered the least number of hours observing since December 2002.

The unusual object with provisional designation 6R10DB9 made it's fourth and final perigee in June. Back during the March perigee it was observed with the 10-m SALT telescope and found to have a rotation period of only 2.75 minutes and an amplitude at that time of 1.2 magnitudes. This time it approached from the sunward side of the Earth, passed over the North pole and was picked up again a day after perigee on June 15th in Draco, about 1 degree from Theta Cep while only 0.80 Lunar Distances from Earth, magnitude +19 - +20 and moving at 47"/min. Never 'bright', it was recorded at mag +18.6 on June 18th and at about +19.5 on the 20th, fading again as it receded from both Sun and Earth. The only other observations reported at the time of writing are radar detections from Goldstone on June 12 & 14 and optical astrometry from the 1.5-m Mt Lemmon telescope on June 22. By the end of June it was below 20th mag and too far south to attempt from the UK.

The main indicator that this object is likely to be natural rather than a piece of artificial space junk come from determinations of solar radiation pressure (SRP) acting on it. Bill Gray's FindOrb freeware program includes routines to calculate SRP, given as the area-to-mass ratio or AMRAT in m^2/kg. With astrometry extending for 10 months now, it gives a value of 0.0011, with an RMS residual from 132 observations of 2.5". Not including SRP increases the RMS residual to an unsatisfactory 9.1". The JPL Horizons orbit solution which also includes the Goldstone Radar observations, gives an even smaller value of AMRAT of 0.0007. In comparison, various distant artificial satellites, such as IMP8, Geotail, J002E3 (the piece of old Apollo hardware discovered by Bill Yeung in 2003), WMAP etc have values between 10 and 50 times larger, indicating that 6R10DB9 is much more massive and much less prone to the perturbing effects of SRP than artificial satellites and is therefore likely to be a rocky body, probably about 4 metres in diameter. There is still a chance that time might be spent at some of the large observatories to get spectra and other measurements during July before it goes out of range completely.

2007 April notes: 2007 HV4, Comet C/2007 H2 Skiff, 2007 HB5

2007-05-08T23:34:00.000+01:00

April provided at least some observing at the telescope on 20 nights, though a fair proportion were of poor quality with haze or moonlight (or both).

Even so there were some notable objects followed. Apollo 2007 HV4 was confirmed on the NEO Confirmation Page during the evening of April 20th, discovered earlier the same day by the Mt. Lemmon operation of the Catalina Sky Survey. When found it was only 5 times further away than the Moon and a difficult discovery at mag +20.5, moving at 14"/min. When confirmed 16 hours later it had already doubled in apparent speed and was about 1 magnitude brighter. Although never brighter than 18th mag, it was followed over the next two nights reaching a speed of over 180"/min during the evening of April 22nd, 5 hours after passing Earth at 1.4 Lunar Distances.

Another NEO Confirmation Page object observed on the evening of April 19th turned out to be an 18th mag comet (later designated C/2007 H2 Skiff), announced the next day by the Minor Planet Center (MPC) on MPEC 2007-H33. The comet was moving north at 3"/min but later, when the images were checked for other moving objects (by stacking for main belt minor planet motion of 0.5"/min in a westerly direction), a minor planet could be seen about 4' north of the comet. The comet passed a mere 23" west of the minor planet at about 23:00 UT that night.

Using Astrometrica and the MPCs Minor Planet Checker web page it could not be matched with a known object, so the next night the unidentified object was picked up again and the details of both nights were sent off to the MPC. The MPC could not ID it with a known object, assigned it provisional designation 2007 HB5 and gave Great Shefford discovery credit for this main belter. This is a good example of making use of the images taken for a different purpose - on the discovery night five other observatories reported positions for C/2007 H2 around the same time as I did, but only one, Juan Lacruz at La Canada (J87) in Spain also reported positions for 2007 HB5 that night.

2007 March notes: 2007 EH, 2007 EK and 6R10DB9

2007-04-06T21:44:00.001+01:00

March was an exceptional month for NEO close approaches, with ten objects observed moving faster than 25"/min, and two observed while inside the distance of the Moon.

In the table below "/min is the apparent speed of the object in arcsec/minute and LD = Lunar distance = 0.00257 AU

Object	March UT	"/min	Distance AU	Distance LD
2007 DJ	01.9	30	0.021	8
2007 DX40	02.1	33	0.028	11
2007 EH	11.1	1,250	0.0011	0.4
2007 EK	13.2	382	0.0018	0.7
2007 EV	15.2	42	0.016	6
2007 EO88	18.8	288	0.0032	1.2
2007 FC3	20.8	142	0.0090	3.5
2007 FG1	22.0	25	0.025	10
2007 FY20	31.9	35	0.018	7
2006 VV2	31.9	57	0.024	9

2007 EH is the fastest natural object I have tracked and is currently the third closest observed approach of a designated minor planet ever (only 2004 FH and 2006 DD1 having had astrometry reported while closer).

It was discovered 44 hours before the close approach and put on the NEO Confirmation page during the afternoon of 9th March, but that evening, with it still unconfirmed I spent some time searching about +/- 0.5 degree around the predicted position but without success. Reviewing the discovery positions from the Catalina Sky Survey, one or two looked somewhat out of step with the others and so an orbit was calculated leaving these out. The resulting prediction was about 1 degree west of the NEOCP prediction and the object was indeed picked up close to that place, allowing the subsequent close approach prediction for the next night to be greatly refined.

The close approach itself was remarkable, to watch images appear on the monitor with the object racing across so fast... at it's fastest speed of 1,250"/min it was 15th mag and covering the field of view of my CCD in 53 seconds, or the diameter of the Moon in less than 1.5 minutes! When first picked up on the evening of the 10th at 19:16 UT it was at RA=11h 41m Dec=+30, reached RA=15h 50m Dec=+60 at 00:45UT on 11th and was last seen at 02:22UT at RA=19h 37m Dec=+50, over 80 degrees of sky covered in less than 7 hours!

Full details of the confirmation, animations from the close approach night and details of the techniques used to measure astrometry of such a fast moving object can be found at http://www.birtwhistle.org/Gallery2007EH.htm.

2007 EK which passed at 0.7 Lunar Distances just two nights after 2007 EH would in a more average month have headlined itself. However, it was nearly two magnitudes fainter than 2007 EH and so was not quite the spectacle of the earlier NEO.

One other noteworthy object seen during the month was 6R10DB9, a Catalina Sky Survey temporary designation given to an object discovered last September which has since then been in geocentric orbit, originally expected to be a small piece of man-made space junk, but increasingly suspected of being natural. It was picked up at mag +19 moving at 24"/min in a dense starfield in Gemini, just 1.2 Lunar Distances from Earth, as it approached it's 2nd to last perigee. It will be perturbed out of the Earth's vicinity for the foreseeable future this coming summer. Attempts to obtain spectra with the 6.5-m MMT during the March perigee were unfortunately clouded out, but there will be one last opportunity in June to try and determine once and for all whether it is indeed a natural object. Some details of the story so far of this interesting object can be found at http://www.birtwhistle.org/Gallery6R10DB9.htm, but hopefully more to come in June and July.

2007 February notes: 2007 BD7, 2007 BZ48 and 2007 DA61

2007-03-06T00:09:00.002Z

The first half of February was reasonably favourable with 8 nights used up to the 14th and 49 hours logged, while the last half of the month was very poor, with just 4 cloud interrupted hours logged over 3 nights.

Apollo object 2007 BD7 discovered on 23 Jan 2007 from Lowell was followed on four nights up to 6th Feb as it approached Earth, with it's phase angle reaching about 90 degrees on the last night. It was moving swiftly into evening twilight and with the phase angle continuing to increase and magnitude fading rapidly it was not seen again.

Another Apollo 2007 BZ48, discovered by the Mt. Lemmon Survey in January and making a close approach in February, was also observed on four nights, last seen on the morning of the 7th within hours of it passing Earth at 4.5 Lunar distances at a moderately fast 56"/minute.

The only object imaged from the NEO Confirmation Page in the last half of the month was 2007 DA61, during a half hour gap in the clouds on 25th Feb. This turned out to have a perihelion distance of 2.6 AU, in a highly elliptical orbit, elements available by early March giving P=134 years and indicating perihelion at the beginning of March 2007 (though these values may change somewhat as further positions are obtained). It appeared completely stellar in my images and is likely to be a Damocloid asteroid, but it is possible it might show some signs of outgassing with large instruments in the coming weeks.

2007 January notes: 2007 AG2 = 2004 BO41, 2007 BD

2007-02-06T01:37:00.000Z

A LINEAR discovery added to the NEO Confirmation page on 8th Jan was eventually confirmed from Great Shefford 2 days later at +69 degrees declination in the evening sky and followed for four nights over the next two weeks at magnitude +18/19. Given the designation 2007 AG2, it was strangely not followed up by any other observatories. Then on 25th Jan I heard from Sergio Foglia that he had identified 2007 AG2 with the NEO 2004 BO41 which had been discovered by LINEAR and observed from 19-29 Jan 2004 and co-incidentally I had observed on several dates that apparition as a morning object, eventually being lost in the twilight.

I had searched for 2004 BO41 a year after discovery on 3rd Jan 2005, covering about 1 degree of sky. It turns out that the actual position at that time was more than 12 degrees further on, so even 12 months after discovery it was hopelessly lost and by Jan 2007 was many tens of degrees off track.

Another interesting object this month, 2007 BD was discovered by Eric Christensen at the Catalina Sky Survey using the 0.68-m Schmidt. It was only 3 Lunar Distances away and already 17th mag, moving at 27"/min. It passed inside the Moons orbit 32 hours later, reaching a minimum distance from Earth of 0.84 L.D. on 18 Jan 2007 at 02:53UT and was well observed from the Crimea-Nauchnij, Gnosca and Modra observatories and also from the Catalina Sky Survey during the 16 hours it remained inside the Moons orbit. It was last caught from Modra 42 minutes before closest approach, travelling at 303"/min at mag +13.
It was then picked up again from Catalina 52 minutes after closest approach.

Unfortunately, during the close approach I was clouded out, but did manage to catch it 2 nights later when it was still about mag +19 and moving at 11"/min. This is quite unusual to be visible for several days on each side of an approach within the orbit of the Moon. It turns out that 2007 BD is an Aten minor planet with an orbit smaller than the Earth's, taking just 230 days to circle the Sun and with an aphelion distance of 0.986 AU it could be argued to be an Apohele (orbit being entirely inside that of the Earth). However, with the Earth at perihelion in January and the object reaching aphelion literally on the day of close approach, it was overtaken by Earth, passing just 200,000 miles outside the Earths orbit, appearing to approach from almost due East and to recede due West so was therefore almost equally well placed for observers for days either side of close approach.

2006 December notes: Observing statistics

2007-01-07T01:23:00.001Z

After a very good November, the weather in December was much poorer. Only ten nights were usable with several of those being near the Full Moon. Ten consecutive cloudy nights over the Christmas break was the longest cloudy period at Great Shefford since the start of 2004. 14 objects were observed off the NEO confirmation page, along with another 15 NEOs, all but a couple were observed just on single nights.

Stats for 2006 (2005) show a slight reduction in clear nights from the previous year, but an increase in the number of images taken, due mainly to the upgrading of the CCD in Sep 2005 to allow faster image download times. Images were taken on 169 (181) nights, while the number of hours spent observing was 798 (841). However, 80,515 (69,239) images were taken, with the CCD shutter being open for a total of 507 hours (438 hours) over the year.

2006 November notes: 2006 WV

2006-12-05T01:56:00.001Z

November ended up providing the most observing time at Great Shefford since Nov 2005, 105 hours over 16 nights.

The NEO highlight of the month was 2006 WV, discovered on Nov 17th with the 0.68-m Schmidt at Catalina. At 20th mag and moving at a moderate 2"/min at discovery it was added to the NEO confirmation page and was searched for on the evening of Nov 18, but not found. Unusually it was outside the uncertainty area predicted by the Minor Planet Center, reason being that it had unusual motion because it was headed almost directly for us and was accelerating rapidly towards a very close encounter at 10am on 21 Nov, within the orbit of the Moon.

LINEAR and the Mt. Lemmon telescope of the Catalina Survey picked it up again less than 24 hours later and it was observed from Great Shefford on Nov 19.0 UT, moving at 6"/min and at mag +19. The next night was cloudy, but by 9pm on 20th Nov it had brightened up to mag +16.5 and was racing along at 150"/min! By this time it was about double the distance of the moon and closing fast. It was followed on and off all night, finally lost to the morning twilight at 6:47am on 21 Nov with the Sun just 7 degrees below the horizon, by which time it was moving at 414"/min (or the apparent diameter of the moon in about 4 minutes), mag +15 and just at the point of crossing inside the moons orbit. Although not reported again, closest approach was 3 hours later at a distance of 349,900 Km (0.91 Lunar distances).

2006 October notes: 2006 RZ and 2006 TA8

2006-11-06T00:10:00.001Z

The month started off with Apollo 2006 RZ (mentioned last month) passing close by the Earth on Oct 6/7. It was tracked on the 6th until about 20:15UT, moving at 86"/min at 15th mag. those positions being the last reported of the object. However, it was picked up again 4.5 hours later, through a gap in the trees, just 10 degrees above the north horizon, moving very obviously between frames. By then it was at the unusually large phase angle of 119 degrees, but unfortunately there were too few comparison stars visible in the images to measure positions.

A number of good nights during October were used to go for some very faint NEOs, an increasing number of which are being put on the NEOCP, mainly by the Catalina and Spacewatch surveys. However, there were also a proportion of bright and often fast moving objects discovered, including 2006 TA8, discovered by LINEAR at high northern declinations on Oct 12 and followed as a 16th mag object on Oct 13, 17 & 22 from Great Shefford, after which it disappeared south in the morning sky.

2006 September notes: 2006 RZ, 2006 SU49 and 2006 SO198

2006-10-05T17:06:00.002+01:00

Generally poor weather continued here during September, still, some work was done on 14 nights, but again few long runs on any particular object could be done.

2006 RZ is a relatively rare amateur NEO discovery, having been picked up at 18th mag by H. Michels from Herrenberg on Sep 4th. It was followed from early September through to the end of the month, passing about 5 lunar distances away in the first week of October having brightened to mag 14.

Some other interesting objects were followed, 2006 SU49 being posted as an impact risk at Torino scale 1 for a number of days before being removed after being found on old NEAT and Sloan archive images going back 5 years.

2006 SO198 was discovered by LONEOS on Sep 29 and was confirmed from Great Shefford while on the NEOCP. It was at the 'fast' end of it's uncertainty area, mag 18 and moving at about 3"/min, about 11' away from the prediction. Less than 4 days later it was to make a pass just outside the orbit of the moon. It was last seen the day before at 16th mag moving at 30"/min, but would have been 14th mag and moving at 800"/min at closest, but it would have been only visible from S. Africa-India and was not reported.

2006 August notes: 2006 ON1, 2006 QV89, 6Q0B44E

2006-09-05T00:52:00.001+01:00

Although some work was done on 16 nights in August, many sessions were interrupted by cloud with just a couple of nights judged as good. Most of the NEOs followed were observed on single nights only, the exception being Apollo 2006 ON1 with three nights.

Apollo 2006 QV89 was observed while it was on the NEOCP and is interesting because its minimum orbital intersection distance with the Earth (MOID) is currently given as 0.00001 AU or about 1,000 miles. At the time of writing (Sep 5th) it is listed with a 1 in ~800 chance of collision with Earth in 2019, so just as well it is only about 30 metres in diameter... Further positions in the coming days are desirable.

On Aug 29th positions for 6Q0B44E were obtained, discovered by the Catalina survey the day before and subsequently found to be in an unstable 80 day orbit around the Earth. It is still unclear whether this is an artificial satellite re-captured by the Earth similar to the Apollo 12 S-IVB third stage J002E3 back in 2003 or whether it is a very small (1-5 metre diameter) NEO temporarily captured by Earth. As noted by Bill Gray, with the current data, it looks as if this object probably entered the Earth/Moon system sometime between about 2000 and 2003, though dates as far back as 1991 are quite possible. Paul Chodas (JPL) comments that it will stay in Earth orbit for at least three more years.

2006 July notes

2006-08-01T21:34:00.000+01:00

With the summer monsoon having taken hold in the southern USA, stopping the big surveys from operating for most of the month, time was spent catching some NEOs at their second and subsequent oppositions.

Working with Roger Dymock we also went after some more normal main belt minor planets on the FUAP (Follow Up Astrometric Program) target list at http://asteroidi.uai.it/ which is maintained by Sergio Foglia on behalf of the UAI Minor Planets Section. This site lists minor planets of mag +18.5 or brighter that are in need of observation, whether newly discovered and under-observed, or awaiting recovery at their second or subsequent oppositions.

The last week of the month saw a flurry of NEO discoveries from the surveys in a brief respite from their bad weather, with several objects at mag 16-17.

2006 June notes: 2006 KZ112 and 2006 MU6

2006-06-28T08:41:00.000+01:00

Several objects were followed over a period of a couple of weeks during the month, including 2006 KZ112 which has an interesting 'Encke like' orbit (2006 KZ112: q=0.29, e=0.89, i=38, P=4.0, Encke: q=0.33, e=0.85, i=12, P=3.3).

Of the other objects observed, 2006 MU6 was picked up on June 27 after being discovered by Spacewatch on June 20th and is a possible Mars Trojan (though the uncertainties on the orbital elements are still large). Already very faint it is predicted to fade quickly.

2006 May notes: 2006 JE, 2006 GY2, 2006 HX57, 2006 JV26 and 2006 JF42

2006-06-03T20:47:00.000+01:00

May was on the way to being my worst month since Nov 2003 until the unsettled spell finally ended on 27 May and four of the last five nights were clear.

The month had started well with some fast movers - 2006 JE was a LINEAR discovery that I managed to confirm when it was on the NEOCP, about 1/2 degree off track and moving at 94"/min. A much easier target because it was over 4 mags brighter at +14.0 but travelling at about the same speed was 2006 GY2 on May 15.9, just a few hours before it passed 7 lunar distances from Earth and the same time as it was being observed from Arecibo and Goldstone and found to be a binary with components of 400 m and 80 m diameter. 2006 HX57 was observed on May 6.0 at mag 16.5, moving at 92"/min and also 2006 JV26 on May 8.9 at mag 16.5 and moving at 290"/min, less than 3 lunar distances away.

An interesting object discovered on May 11 by the Catalina Sky Survey was 2006 JF42, observed from May 15-31, deep in the glow of evening twilight. It has a very short period of only 201 days (shorter than Venus) but with an eccentric orbit taking it from 0.28 AU at perihelion to 1.06 AU at aphelion, with the most favourable viewing circumstances being when aphelion occurs around May 21, when it would be placed in the opposition region of the sky south of the ecliptic. This year aphelion was only two weeks later but the best elongation achieved was only 96 degrees.

2006 April notes: Integral, 2006 GA, 2006 GC, Comet 73P/Schwassmann-Wachmann

2006-05-05T20:27:00.012+01:00

April was a much better month than the last few, with 19 usable nights.

The artificial satellite Integral wandered into the field of component 73P-N/Schwassmann-Wachmann on the morning of April 12th, moving at about 230"/min. Not knowing whether it was a close approaching NEO or a very unusual artificial satellite I followed it for 50 minutes until it ran into bright twilight, which was long enough to work out an orbit for it and to pick it up again 2 nights later. Thanks go to Tony Beresford and Mike McCants for identifying it for me.

Artificial Satellite Integral passes through the field of view of faint fragments of comet 73P/Schwassmann-Wachmann

A couple of NEOs were followed for several weeks (2006 GA & 2006 GC) but most were observed for much shorter arcs. A fair proportion of the early mornings during the month were spent imaging over 30 of the components of 73P as it approached the Earth.

2006 January notes: 2006 BA, 2006 BV39, 2006 BF56, 2006 BH99

2006-02-04T01:54:00.009Z

The first half of January was very poor with just 3 usable nights, but the second half was better with 10 nights and brought some interesting fast movers...

On Jan 20/21st 2006 BA was observed at mag +16.5, passing by at 2 lunar distances (l.d.) and moving at 60"/min.

Then on Jan 26th the Spacewatch 1.8-m reflector discovered 2006 BV39, confirmed 15 hours later from Klet in the Czech Republic. It was about 4 l.d. at discovery and closing fast. In conversation with Monty Robson at 932 (John J. McCarthy Observatory in Connecticut) on the morning of the 27th I mentioned that 2006 BV39 would be an interesting target the next night. Nowhere had reported it to the Minor Planet Center after Klet's confirmation when I tried but failed to find it at midnight on the 28th. On checking with Monty, he mentioned that he had got it the night before but had not reduced the astrometry. He kindly measured the positions immediately and sent them through to me, allowing me to update the ephemeris and then to locate the NEO. It was 23' W of the MPC's prediction and would have been very difficult to find without the correction. By this time it was moving at 210"/min and was just 5,000 miles outside the Moon's orbit. I followed it until 05:14UT on the 29th by which time it had accelerated to 277"/min and had crossed 28,000 miles inside the Moon's orbit with closest approach about 2 hours later at 0.9 l.d. This was the third NEO I have tracked while inside the Moon's orbit in four months!

Just a few hours later news came through of a mag +21 NEO discovered from Mt. Lemmon with the 1.5-m reflector at 7:22UT and followed by them for 5 hours, during which time the apparent speed went from 10"/min to 14"/min. Obviously approaching fast, it was confirmed almost simultaneously from Klet and Great Shefford at about 22:10UT that night and given the designation 2006 BF56 by the Minor Planet Center. By then it was mag +19.5, moving at 48"/min and was about 3 l.d. away. It was followed from Great Shefford until 06:42UT when it was lost in morning twilight, by which time it was about mag +17.5, had accelerated up to 346"/min and was only 23,000 miles outside the Moon's orbit. It crossed inside the Moon's orbit just 15 minutes later and closest approach was at 10:32UT when it passed at 0.5 l.d. Although not reported after 06:42UT it was anyway unobservable by 12:00UT on 29th, having faded back to mag +21 again but also moving at 1,000"/min! The entire apparition was over in less than 1.5 days during which time it had covered nearly 180 degrees of sky.

Although badly hampered by cloud, 2006 BH99 was then observed on the night of Jan 30 at mag +17 at 2.7 l.d., moving at 90"/min, passing by at just 1.2 l.d. about 14 hours later. Quite a busy few days!

2005 December notes: 2005 YQ96, 2005 YW

2006-01-02T22:25:00.003Z

There were not many long observing runs on NEOs during December, but probably the most interesting result was helping confirm the discovery of 2005 YQ96 on December 30th, which with an aphelion distance of 0.992 AU makes it the 6th known "Apohele", or Minor Planet with it's orbit completely inside the Earth's orbit.

Also, 2005 YW discovered on December 21 was examined carefully on a couple of nights for signs of cometary activity but it appeared stellar in a 26 minute exposure in good conditions on the 28th. This object has a period of about 2000 years and with perihelion at 2.0 AU due next winter it is possible it may eventually show activity. Unfortunately it will be lost in twilight this coming spring and will pull away from the Sun next winter but at far southerly declinations, not visible from the UK.

2005 November notes: 2005 WC, 2005 VX3, 2005 WY3, 2005 WN3, 2005 WY, GS5BRH

2005-12-03T23:53:00.002Z

November was an exceptional month for me, not so much the 16 usable nights, but the CCD shutter was open for 74 hours in total. A number of objects turned out to be interesting:

2005 WC was confirmed here after it was posted on the NEOCP following discovery by LINEAR, moving at 75"/min. Richard Miles also managed to get some positions of it that night as it headed quickly towards the north horizon. Richard's and my positions were the only follow-up reported in the world before it went out of view less than 24 hours later.

2005 VX3 was a very faint object observed while on the NEOCP and was finally announced as having a period of 32 years based on observations from Nov 1-6th. Subsequent observations from Great Shefford on Nov 13 and 21 showed it to have a very much longer period, possibly even being in a hyperbolic orbit.

2005 WY3 was another very faint and slow moving object observed while on the NEOCP and it ended up being determined to be about 6AU from the Earth. With a period of 19 years, q=1.8 and reaching perihelion in about 3 years it will be interesting to keep an eye on this one.

An object discovered by the Mt Lemmon Survey on Nov 25 and rapidly approaching Earth was (just!) caught on the edge of 5 consecutive frames, moving at 175"/min. This was enough to confirm the object and it then received the designation 2005 WN3. It turned out to be just inside the Moons orbit when I imaged it and passed just 6.5 Earth diameters away less than 5 hours later, less than a month after catching 2005 UW5 inside the Moon's orbit.

While imaging fast moving NEO 2005 WY on the morning of Nov 27, another even faster moving object was recorded speeding through at 294"/min, staying in the field of view for 3m 46s on 35 separate frames, but unfortunately I didn't spot it on the images until the next evening, by which time it was hopelessly lost. After positions were measured, assuming it might be an artificial satellite I tried fitting a geocentric orbit to the positions but none of the solutions were tenable (with perigee always smaller than the Earths radius). I gave it temporary name GS5BRH and sent the positions to the Minor Planet Center and heard back that they couldn't match to any known satellite and that although some of the residuals were up to 6" or even 8", it may have been about 0.002 AU from Earth at the time.

2005 October notes: 2005 UH5, 2005 UW5, 2004 FH

2005-11-09T23:15:00.002Z

There were several highlights this October, I managed to catch 2005 UH5, the NEO that Roger Dymock found in the online FMO project images on 27 Oct. It was quite a difficult object through high cloud, I searched for it over multiple fields on the night but didn't identify it until the next day. Congratulations to Roger!

Then on 29th Oct I managed to follow 2005 UW5 while it was inside the orbit of the Moon, which is a first for me. I first picked it up through gaps in clouds at 18:46 UT when it was moving at 330"/min and when last seen at 21:19 UT it had accelerated to 525"/minute. At that time it was only 17 Earth diameters away!

An 11 frame animation of 30 seconds of motion between 21:12:00 -21:12:30 UT on 29th October. Each frame is a 1 second exposure and the animation plays back in real time, exactly as the images were taken, with a 2 second gap between frames. The field of view is 18.3'x18.3'

Of the NEOs with reliable orbits that are known to have had close approaches to the Earth, this approach was the 16th closest ever, but in fact only one of the other 15 (2004 FH) was actually observed while it was closer to the Earth than 2005 UW5 was on 29th October.