tag:blogger.com,1999:blog-32110736653535867082024-02-07T03:03:43.846+00:00Inside Great Shefford ObservatoryPeter Birtwhistlehttp://www.blogger.com/profile/13429846157607762259noreply@blogger.comBlogger75125tag:blogger.com,1999:blog-3211073665353586708.post-87712447689702224432016-03-22T23:22:00.000+00:002016-03-22T23:22:30.662+00:00Slight cometary activity detected in tiny comet P/2016 BA14 (PANSTARRS)Comet P/2016 BA14 was originally reported as a minor planet when discovered by the 1.8-m Pan-STARRS1 telescope on 2016 January 22 but further images taken with the 4.3-m Discovery Channel Telescope on 2016 Feb. 10.2 and 13.2 UT showed a tail about 10" long in p.a. 65 degrees. It is very likely that P/2016 BA14 is a small fragment of comet 252P/LINEAR, both comets making close approaches to Earth during March 21-23 2016.<br />
<br />
With the comet moving from far south declinations swiftly northward during mid to late March the night of the full moon, March 22 was the first opportunity to image this tiny comet from Great Shefford, coincidentally the date of closest approach to Earth, with the comet at slightly less than 10 times the distance of the moon.<br />
<br />
The images below were taken with P/2016 BA14 just 37 degrees from the full moon and some interference from passing high cloud too. Each frame is made from a stack of between 80 and 94 individual 6 second exposures and all stacked frames show weak cometary activity extending to the south east of the nucleus (to the lower left) between p.a. 120 - 170 degrees. The best stacks show indications of a tail at least 3.5 arcmin long in p.a. 147 degrees. The anti-solar direction is in p.a. 126 degrees.<br />
<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: left; margin-right: 1em; text-align: left;"><tbody>
<tr><td style="text-align: center;"><a href="http://www.birtwhistle.org.uk/images/PBirtwhistle_P2016BA14_20160322_1926_2056.gif" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" src="http://www.birtwhistle.org.uk/images/PBirtwhistle_P2016BA14_20160322_1926_2056.gif" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Comet P/2016 BA14 showing weak cometary activity on 2016 March 22.</td></tr>
</tbody></table>
<br />Peter Birtwhistlehttp://www.blogger.com/profile/13429846157607762259noreply@blogger.com0tag:blogger.com,1999:blog-3211073665353586708.post-71848102086048660092015-11-14T00:12:00.000+00:002015-11-14T00:12:05.743+00:00The life and death of WT1190F (= UDA34A3 = UW8551D = 9U01FF6)<div style="text-align: justify;">
An object discovered by the Catalina Sky Survey and assigned the designation WT1190F initially looked very much like a near-earth asteroid when added to the NEO Confirmation Page (NEOCP) on 3rd October 2015 but it was removed by the Minor Planet Center two days later with the note "Was not a minor planet". The astrometry at that time showed it was orbiting Earth every 21 days in a very unusual and elongated orbit taking it to within one Earth radius of the surface of the Earth at perigee but 1.65 times further away than the Moon at apogee. The eccentricity (e) of the orbit was 0.96.</div>
<div class="separator" style="clear: both; text-align: center;">
<br /></div>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://www.birtwhistle.org.uk/images/WT1190F_20151024_213828_2_2x2_01+78A.bmp" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://www.birtwhistle.org.uk/images/WT1190F_20151024_213828_2_2x2_01+78A.bmp" height="249" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">WT1190F captured during its penultimate close pass with the Earth, three weeks before impact</td></tr>
</tbody></table>
<div class="separator" style="clear: both; text-align: center;">
<br /></div>
<div class="separator" style="clear: both; text-align: justify;">
Even while it was still on the NEOCP I had been in contact with Bill Gray, the author of Guide and also of FindOrb, because the orbit appeared similar to an unidentified object picked up in October 2009 (9U01FF6) and also to an object discovered in February 2013 (UDA34A3) that Bill had subsequently managed to link to another discovery in November later the same year (UW8551D).</div>
<div class="separator" style="clear: both; text-align: justify;">
<br /></div>
<div class="separator" style="clear: both; text-align: justify;">
9U01FF6 was in a ~25 day orbit with e=0.83 at discovery and had been followed for a couple of days by a number of observatories. I had then managed to follow it at a further five perigees up to May 2010 and had written about it in <a href="http://peter-j95.blogspot.co.uk/2009/10/2009-october-notes-2009-tm8-2009-ud.html" target="_blank">Oct</a>, <a href="http://peter-j95.blogspot.co.uk/2009/12/2009-november-notes-2009-vx-2009-vz.html" target="_blank">Nov</a> and <a href="http://peter-j95.blogspot.co.uk/2010/01/2009-december-notes-2009-wz104-9u01ff6.html" target="_blank">Dec</a> 2009.</div>
<div class="separator" style="clear: both; text-align: justify;">
<br /></div>
<div class="separator" style="clear: both; text-align: justify;">
UDA34A3 (= UW8551D) was in a 29 day orbit with e=0.86 in February 2013. Bill's linkage between the two 2013 objects was remarkable, as UDA34A3 was only observed for 5 hours in February and UW8551D for less than 2 hours in November! </div>
<div class="separator" style="clear: both; text-align: center;">
<br /></div>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://www.birtwhistle.org.uk/images/WT1190F_20151113_053428_20_2x2_1A.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://www.birtwhistle.org.uk/images/WT1190F_20151113_053428_20_2x2_1A.jpg" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">WT1190F less than 1 hour from impact with the Earth, showing regular rotational light variations every 3/4 second</td></tr>
</tbody></table>
<br />
<div style="text-align: justify;">
Bill pointed out on 5th Oct. 2015 that calculating the orbit of WT1190F forwards showed that it would impact the Earth on 13th November 2015! Subsequent astrometry confirmed this, impact occurring less than 10 miles south of Sri Lanka at 06:19 UT on 13 Nov. 2015, in daylight, around noon local time.</div>
<div style="text-align: center;">
<div style="text-align: justify;">
<br /></div>
</div>
<div style="text-align: justify;">
Bill eventually managed to show that WT1190F was the same object as UDA34A3 = UW8551D from 2013, though he faced considerable difficulties due to the effects that solar wind has on this apparently very low mass object, together with close approaches to the Moon. Bill then requested if both the Catalina and PanSTARRS surveys could search their archives using the new linkage to see if they could find any further images of WT1190F going back that might link up with 9U01FF6 from 2009. PanSTARRS managed to locate and measure images going back to December 2012 but even with these, attempts to link the 2012-2015 apparitions back to the 2009/10 observations of 9U01FF6 proved impossible.</div>
<div style="text-align: justify;">
<br /></div>
<div style="text-align: justify;">
However, Bill then figured that maybe the prediction from the 6 months of observations of 9U01FF6 from 2009 might be good enough for the surveys to locate images extending the arc <i>forwards</i> from 2009 to try and join the two arcs up that way and indeed both Catalina and PanSTARRS managed to find it in their archives from January and April 2011. The April positions were crucial as a lunar flyby in February 2011 had made the orbital elements very uncertain after that date. With the new positions Bill was able to calculate 9U01FF6 forwards to another lunar flyby on 24 May 2012 and similarly calculate WT1190F back to the same flyby and prove they were indeed the same object. Have a look at the very comprehensive FAQ provided by Bill Gray <a href="http://www.projectpluto.com/temp/wt1190f.htm" rel="nofollow" target="_blank">here</a>.<br />
<br /></div>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://www.birtwhistle.org.uk/images/WT1190F_20151113_055835_1_2x2_2A.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://www.birtwhistle.org.uk/images/WT1190F_20151113_055835_1_2x2_2A.jpg" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">The streak on the left is the final image captured from Great Shefford before WT1190F disappeared below the horizon, 20 minutes before impact over the Indian Ocean</td></tr>
</tbody></table>
WT1190F is thought likely to have been part of an old lunar mission and from the way it was easily blown around by the solar wind it is probably hollow and 1-2 meters in size, possibly something like the <a href="https://en.wikipedia.org/wiki/Lunar_Prospector" target="_blank">Lunar Prospector TLI stage</a> from 1998.<br />
<br />
A team from ESA observing from an aircraft over the Indian Ocean witnessed it burn up in the atmosphere exactly as predicted, this image and more details can be found at their page <a href="http://www.seti.org/seti-institute/news/seti-institutes-peter-jenniskens-observes-wt1190f-air" rel="nofollow" target="_blank">here</a>.<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://i2.wp.com/www.universetoday.com/wp-content/uploads/2015/11/WT-reentry-fireball-tight.jpg?resize=580%2C372" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" src="http://i2.wp.com/www.universetoday.com/wp-content/uploads/2015/11/WT-reentry-fireball-tight.jpg?resize=580%2C372" height="256" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><span style="background-color: #eeeeee; color: #111111; font-family: "lustria" , "arial" , sans-serif; font-size: xx-small; line-height: 22px;">When WT1190F struck this atmosphere over the Indian Ocean around 6:20 Universal Time (12:20 a.m. CST) today , it broke apart into multiple fireballs against the blue sky. The object came down around 1:20 p.m. local time. Credit: IAC/UAE Space Agency/NASA/ESA</span></td></tr>
</tbody></table>
<br />Peter Birtwhistlehttp://www.blogger.com/profile/13429846157607762259noreply@blogger.com2tag:blogger.com,1999:blog-3211073665353586708.post-68118409021260215322013-10-10T00:05:00.001+01:002013-10-10T00:10:24.956+01:00Juno spacecraft captured on its way to JupiterThe Juno spacecraft made a very close approach to Earth on 9th October 2013 at 19:21 UT, passing just 560 km above the sea near South Africa, before swinging around and heading out for Jupiter.<br />
<br />
The images here were captured between 20:23:33 UT and 20:24:47 UT with Juno at an altitude of just 14 degrees, soon after it rose above the horizon, just over an hour after the close approach. Exposures were limited to 1 second to freeze the motion and allow positions to be measured.<br />
<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://www.birtwhistle.org.uk/images/Juno_20131009_2023-PBirtwhistle.gif" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" src="http://www.birtwhistle.org.uk/images/Juno_20131009_2023-PBirtwhistle.gif" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Juno spacecraft 1 hour after close approach, moving at 800"/minute and at a distance of 42,500km from the observatory. </td></tr>
</tbody></table>
Here a 20 second exposure shows Juno streaking in front of the distant stars, already much slower moving and more distant than the image above.<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://www.birtwhistle.org.uk/images/Juno_20131009_205510_20-PBirtwhistle.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" src="http://www.birtwhistle.org.uk/images/Juno_20131009_205510_20-PBirtwhistle.jpg" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Juno spacecraft, 20 second exposure starting at 20:55:10 UT, moving at 370"/minute and at a range of 62,800km</td></tr>
</tbody></table>
<br />Peter Birtwhistlehttp://www.blogger.com/profile/13429846157607762259noreply@blogger.com1tag:blogger.com,1999:blog-3211073665353586708.post-79318365376044402412013-02-20T02:22:00.001+00:002013-10-09T23:40:35.359+01:00Partial lightcurve for 2012 DA14On the night after <a href="http://peter-j95.blogspot.co.uk/2013/02/2012-da14-makes-its-very-close-fly-by.html">closest approach</a>, when the apparent motion had slowed down to around 15"/min and magnitude faded to about +15, three hours of photometric observations were obtained, the diagram below indicating that just a part of the overall rotational lightcurve had been captured, showing a rise to magnitude +14.3R, followed by a fall to +15.9R.<br />
<br />
<a href="http://www.jpl.nasa.gov/news/news.php?release=2013-063" target="_blank">Radar results for 2012 DA14</a> obtained from NASA's Goldstone facility and qualified by Dr. Lance Benner on <a href="http://tech.groups.yahoo.com/group/mpml/message/28120" target="_blank">MPML</a> indicate a rotation period of "probably somewhat longer than 8 hours".<br />
<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://www.birtwhistle.org.uk/images/PBirtwhistle_2012_DA14-Raw.PNG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="300" src="http://www.birtwhistle.org.uk/images/PBirtwhistle_2012_DA14-Raw.PNG" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">2012 DA14: 3 hours of lightcurve covering 2013 Feb. 16th 21:10 UT - 17th 00:11 UT<br />
PPMXL catalogue used for reductions, error bars derived from measured S/Nr are shown</td></tr>
</tbody></table>
<br />
Update 20/2/2013 20:35UT: A much more complete lightcurve by Bruce Gary from Hereford Arizona Observatory (<a href="http://www.brucegary.net/HAO/" target="_blank">G95</a>) can be seen <a href="http://brucegary.net/2012DA14/" target="_blank">here</a>, covering about 10 hours of observing, yielding a rotation period of just over 9 hours.Peter Birtwhistlehttp://www.blogger.com/profile/13429846157607762259noreply@blogger.com0tag:blogger.com,1999:blog-3211073665353586708.post-69553044769724492522013-02-15T23:21:00.000+00:002013-10-09T23:41:10.496+01:002012 DA14 makes its very close fly-by of Earth<br />
2012 DA14 captured on its way out from its very close encounter with Earth.<br />
<br />
The NEO was 8th magnitude and moving at 1,645"/minute when these images were obtained and was nine times closer than the Moon. At its closest at 19:24 UT on 15th Feb. 2013 it had come inside the geostationary satellite ring but by the time these images were taken 80 minutes later it had already passed back outside.<br />
<br />
<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://www.birtwhistle.org.uk/images/2012DA14_20130215_204715-204737-PBirtwhistle.gif" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" src="http://www.birtwhistle.org.uk/images/2012DA14_20130215_204715-204737-PBirtwhistle.gif" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">2012 DA14 1hour and 20 minutes after closest approach to Earth</td></tr>
</tbody></table>
<br />
Exposures were limited to 0.2 seconds to stop the asteroid from trailing so the images could be used to measure the object's position.<br />
<br />
A few gaps in thickening clouds only allowed a short run of images to be captured between 20:43 - 21:00 UT, before the sky completely clouded over.Peter Birtwhistlehttp://www.blogger.com/profile/13429846157607762259noreply@blogger.com0tag:blogger.com,1999:blog-3211073665353586708.post-27626670490816641532012-12-11T03:29:00.000+00:002013-10-09T23:41:38.603+01:00NEO 2012 XE54 eclipsed by Earth shadow<div class="separator" style="clear: both; text-align: left;">
As predicted by Pasquale Tricarico on the Minor Planet Mailing List in message <a href="http://tech.groups.yahoo.com/group/mpml/message/27642" target="_blank">27642</a>, NEO 2012 XE54 was eclipsed by the Earth's shadow during its close approach to Earth on 11 December 2012, a relatively rare event. More information from Pasquale <a href="http://orbit.psi.edu/~tricaric/2012XE54.html" target="_blank">here</a>.</div>
<div class="separator" style="clear: both; text-align: left;">
<br /></div>
<div class="separator" style="clear: both; text-align: left;">
A very preliminary lightcurve of the eclipse as measured from images taken at Great Shefford Observatory is given below, with the details subject to revision later. The measurements are from individual images apart from the points at mid-eclipse, measured from stacks of multiple images.</div>
<div class="separator" style="clear: both; text-align: center;">
<a href="http://www.birtwhistle.org.uk/images/2012XE54Eclipse-J95.png" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" src="http://www.birtwhistle.org.uk/images/2012XE54Eclipse-J95.png" /></a></div>
<br />Peter Birtwhistlehttp://www.blogger.com/profile/13429846157607762259noreply@blogger.com1tag:blogger.com,1999:blog-3211073665353586708.post-83116474525422847532012-09-04T20:47:00.000+01:002013-10-09T23:42:07.422+01:00Distant Comet C/2012 Q1 (Kowalski)<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://www.birtwhistle.org.uk/images/PBirtwhistle_C2012Q1_20120902.gif" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" src="http://www.birtwhistle.org.uk/images/PBirtwhistle_C2012Q1_20120902.gif" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Comet C/2012 Q1 (Kowalski) taken 2012 Sep 02.01UT<br />
2 images showing movement in 23 minutes.<br />
Each frame is a 16 minute exposure with 0.40-m Schmidt-Cass. telescope & CCD<br />
Original scale 2.14"/pixel, enlarged x4, field size 3.5x3.5 arcmin, North up<br />
(c) P. Birtwhistle 2012, Great Shefford Observatory (J95)</td></tr>
</tbody></table>
Comet C/2012 Q1 (Kowalski) was discovered by Richard Kowalski using the 1.5-m Reflector on Mt Lemmon as a 19th magnitude object in Pegasus on 28 August 2012, 3 days before full moon. He described it as having a faint round coma approximately 20" in diameter (about double the diameter visible in the animation above).<br />
<br />
The full moon hampered the recovery of the discovery and the images above were obtained 2 days after full moon, the very bright sky and interference from high cloud causing a very bright and uneven background to the images.<br />
<br />
At the time of writing, with just a week of positions measured for the new comet, it appears to be between 8-10 AU from Earth and 9-11 AU from the Sun, though any determination of its orbit is necessarily very uncertain without a much longer span of observations. However, at such a great distance, the coma size must be impressive, equating to about 150,000 km diameter.Peter Birtwhistlehttp://www.blogger.com/profile/13429846157607762259noreply@blogger.com1tag:blogger.com,1999:blog-3211073665353586708.post-21132819777980267512012-09-02T23:30:00.000+01:002013-10-09T23:43:54.149+01:00The faint tail of Comet P/2012 NJ (La Sagra)Comet P/2012 NJ (La Sagra) was originally designated as an asteroid when announced by the Minor Planet Center on <a href="http://www.minorplanetcenter.net/mpec/K12/K12N19.html" rel="nofollow" target="_blank">MPEC 2012-N19</a> as 2012 NJ. It had been discovered by the <a href="http://www.lasagraskysurvey.org/index.html" rel="nofollow" target="_blank">La Sagra Sky Survey</a> team from the mountains of Andalucia, Southern Spain early on 13 July 2012 and appeared to be physically unusually big for a newly discovered NEO these days, estimates of its size, derived from assumed asteroidal values of its albedo or reflectivity indicating a diameter of approximately 4-12 km. Coupled with an unusual orbit, inclined almost perpendicular to the Earth's orbit and very elongated, with perihelion just inside Mars' orbit at 1.29 AU but with aphelion further out than Saturn's orbit, it could well be expected to be a comet but none of the initial observers reported any cometary activity, several observers using telescopes of 0.5 - 0.6-m diameter.<br />
<br />
However, on July 18th circular <a href="http://www.cbat.eps.harvard.edu/iau/cbet/003100/CBET003178.txt" rel="nofollow" target="_blank">CBET 3178</a> <span style="font-size: xx-small;">(<a href="http://www.cbat.eps.harvard.edu/services/Subscriptions.html" rel="nofollow" target="_blank">subscription required</a>)</span> was issued, announcing that the object was indeed a comet and re-designating it as Comet P/2012 NJ (La Sagra). Gerhard J. Hahn (Institute of Planetary Research, German Aerospace Center, Berlin) had reported it as
showing a 35" tail in p.a. 235° on stacked and single images taken by
Stefano Mottola using the 1.23-m telescope on Calar Alto on July 16, 17, and 18
UT. A post by Gerhard on the Minor planet Mailing list on <a href="http://tech.groups.yahoo.com/group/mpml/message/27240" rel="nofollow" target="_blank">July 19th</a> gave further details and a link to a document containing images from July 17, 18 and 19th, showing a thin straight tail. An animation of portions of the individual images from that document has been made, used with permission and is shown here:<br />
<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://www.birtwhistle.org.uk/images/P2012NJ_20120717-19_CalarAlto.gif" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" src="http://www.birtwhistle.org.uk/images/P2012NJ_20120717-19_CalarAlto.gif" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Comet P/2012 NJ (La Sagra) on July 17 ,18 & 19th 2012<br />
Images taken by Stefano Mottola using the 1.23-m Calar Alto telescope<br />
(c) Institute of planetary Research, German Aerospace Centre, Berlin</td></tr>
</tbody></table>
<br />
During the days following a few other images showing the tail were posted, including a good sequence covering July 21-25 by Jean-François Soulier from France <a href="http://6888comete.free.fr/fr/imageP2012NJLaSagrafrance.htm" rel="nofollow" target="_blank">here</a>, showing a very faint thin tail.<br />
<br />
The comet reached perihelion at a distance of 1.29 AU from the Sun on 2012 June 14 and reached its closest to the Earth (0.59 AU) on 2012 July 22.<br />
<br />
At Great Shefford Observatory, my first opportunity to image the new comet was on July 21 but with clouds affecting images it was difficult to detect the tail at all. However, on the nights of July 22, 24 and 25 the skies were better and 30 minute sequences of exposures were made once or twice per night to examine the appearance of the tail. Here, 30 minute stacks from the three nights are shown, the original field of view being cropped to 7'x9' and the scale doubled from the original 2.2"/pixel:<br />
<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://www.birtwhistle.org.uk/images/P2012NJ_20120722-25_PBirtwhistle.gif" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" src="http://www.birtwhistle.org.uk/images/P2012NJ_20120722-25_PBirtwhistle.gif" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Comet P/2012 NJ (La Sagra) on July 22, 24 & 25th 2012<br />
0.40-m Schmidt-Cassegrain<br />
Each of the three frames is a stack of 90 x 20 second exposures<br />
(30 minutes total)<br />
(c) P. Birtwhistle, Great Shefford Observatory </td></tr>
</tbody></table>
<div class="separator" style="clear: both; text-align: center;">
<br /></div>
On the night of July 24/25th, 180 images were combined for a total exposure of 1 hour and in the resulting image below the very faint tail can be traced for 6' 30" in p.a. 210°<br />
<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://www.birtwhistle.org.uk/images/P2012NJ_20120724_PBirtwhistle.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" src="http://www.birtwhistle.org.uk/images/P2012NJ_20120724_PBirtwhistle.jpg" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Comet P/2012 NJ (La Sagra) July 25-26 2012<br />
7'x9' field of view, 1 hour exposure<br />
0.40-m Schmidt-Cassegrain<br />
(c) P. Birtwhistle, Great Shefford Observatory</td></tr>
</tbody></table>
<br />
The tail showed a marked drop in brightness between the nights of July 24/25th and 25/26th. An initial sequence of 90 images exposed on the evening of July 25th did not show the tail at all, further sets were obtained later in the night, eventually revealing the faint straight tail. Similar sets the night before had revealed the tail much more readily.<br />
<br />
On 31 July 2012 Artyom Novichonok posted on the Comets Mailing List message <a href="http://tech.groups.yahoo.com/group/comets-ml/message/19737" rel="nofollow" target="_blank">19737</a> that he and Otabek Burhonov had imaged the comet using the 1.5-m f/8 telescope at Majdanak in Uzbekistan with a total exposure of 2.5 minutes a few hours earlier than the image above.<br />
<br />
<div class="separator" style="clear: both; text-align: center;">
<a href="http://www.astronomy.ru/forum/index.php?action=dlattach;topic=91474.0;attach=425691;image" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://www.astronomy.ru/forum/index.php?action=dlattach;topic=91474.0;attach=425691;image" /></a></div>
<br />
The weather stopped any more attempts from Great Shefford before the full moon on 02 Aug 2012 and in the subsequent dark of the moon no further deep attempts were made, the comet itself receding from both Sun and Earth and predicted to be a full magnitude fainter than in the last half of July.<br />
<br />
However, Artyom posted again on the Comets ML with message <a href="http://tech.groups.yahoo.com/group/comets-ml/message/19774" rel="nofollow" target="_blank">19774</a> on 27 Aug 2012 with details of an image taken 2 weeks earlier on 13 Aug 2012 showing a very faint trace of the tail pointing in the anti-solar direction (p.a. 150 deg, down and to the left) and what appears to be a separate tail in p.a. 96 deg, though this second tail has yet to be confirmed.<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://www.astronomy.ru/forum/index.php?action=dlattach;topic=91474.0;attach=433292;image" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" src="http://www.astronomy.ru/forum/index.php?action=dlattach;topic=91474.0;attach=433292;image" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Comet P/2012 NJ<br />
From Majdanak Observatory in Ukbekistan<br />
The tail observed in July is now very faint<br />
and points down and to the left.<br />
Another possible (shorter) tail points to the left,<br />
though this tail is yet to be confirmed.</td></tr>
</tbody></table>
<br />
It is understood that the team at Calar Alto may target P/2012 NJ in mid-September, it will be interesting to see whether any trace of the tail is detectable by then.<br />
<br class="Apple-interchange-newline" />
During the current apparition, the anti-solar direction (the expected direction for an ion tail) rotated from p.a. 242° at discovery, 238-234° during July 16-18, 215° on July 25 and 147° on Aug 14th and those directions agree to within a few degrees of the measured angles from the images above. By mid September 2012 the anti-solar direction will have reached p.a. 100 to 90°.
<br />
<div class="separator" style="clear: both; text-align: center;">
</div>
Peter Birtwhistlehttp://www.blogger.com/profile/13429846157607762259noreply@blogger.com0tag:blogger.com,1999:blog-3211073665353586708.post-65841494848596771462012-07-04T20:05:00.001+01:002012-08-30T19:46:50.965+01:00A decade of operations and a few close approachersThe end of May marked 10 years of operation at Great Shefford Observatory, <a href="http://www.birtwhistle.org/FirstLight.htm" target="_blank">first light</a> occurring on 26 May 2002 with the first astrometry being measured on 30 May 2002, of Comet C/2000 WM1 (LINEAR). In the intervening 10 years I've taken 831,500 images and measured 30,600 astrometric positions of minor planets and comets, with many of the images being taken for photometry rather than astrometry.<br />
<br />
The weather in April and May this year was particularly poor and looking at the <a href="http://www.birtwhistle.org/Statistics.htm" target="_blank">stats</a> over the last 10 years, this April was the worst April in all that time, with only 11 nights usable, nearly half of what would normally be expected. Indeed the 18-night cloudy period from April 23 - May 10 was easily the longest endured here, the previous worst being a period of 12 consecutive cloudy nights in January 2011.<br />
<br />
In what remained of the month there were a number of notable close approachers observed, first up was <b>2012 JU</b>, discovered at 6am UT on May 12th by the Catalina Sky Survey, 31 hours before passing by at 0.53 Lunar Distances (LD). David Briggs at South Observatory, Clanfield (code J84) reported positions during the evening of the 12th at mag +17 and I first picked it up at 23:15 UT, following it for just over 2 hours. In the 3 hours that David and I had it under observation its distance from Earth decreased by 1/5th, to 1.6 LD and its apparent speed accelerated from 60"/min to 90"/min. It was last reported from the Astronomical Research Observatory, Westfield, USA (observatory code H21) at 6h UT on 13th at 1.04 LD, moving at 208"/min at mag +16.<br />
<br />
A much better observed fly-by was <b>2012 KP24</b>, discovered from Mt. Lemmon with the 1.5-m reflector on May 23rd, giving NEO observers the luxury of 5 days warning before closest approach, due at 15:21 UT on May 28th, just 4 Earth diameters from the Earth's surface! At discovery it was mag +21 and 15 LD from Earth. I observed it on four consecutive nights, initially moving at just 1"/min and at mag +20 on May 24/25 but brightening about a magnitude each night. My last measurement was mag +16 in strong twilight at 02:40 UT on May 28th, with it still only moving at 30"/min even though by then it was only 1.5 LD away. It was last reported at 10:24 UT that morning, by the Catalina Sky Survey at mag +14 and moving at 187"/min, 5 hours before closest approach. Sergio Foglia posted on the Minor planet Mailing list a lightcurve derived from observations from H21 that shows a rotation period of 150 seconds and an amplitude of about 1 magnitude for this object, estimated to have a diameter between 13-19 metres.<br />
<br />
However, even before 2012 KP24 was out of the way, the Mt. Lemmon telescope had picked up the next incoming object, <b>2012 KT42</b>. The discovery image was taken just 23h 58m before 2012 KT42 would skim the Earth's surface by a mere 1.1 Earth diameters. As with 2012 KP24 the timing of the close approach would favour observatories in the USA more than those in the UK, with closest approach at 07:07 UT on May 29.<br />
<br />
At discovery 2012 KT42 was at 3.6 LD and within 1.3° of the opposition point, about midway between Antares and Beta Sco and headed almost exactly towards Earth. From Great Shefford it was low in the south that night and I had to wait for it to pass into gaps between trees but eventually managed to image it for a 13 minute period a few minutes after midnight early on May 29th and again from 01:17-02:05 UT. It was mag +15 but only at 13° altitude by 2am.<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://www.birtwhistle.org/images/PBirtwhistle_2012KT42_20120529_013130_4_2x2+76x2.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" src="http://www.birtwhistle.org/images/PBirtwhistle_2012KT42_20120529_013130_4_2x2+76x2.jpg" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">2012 KT42, mag. +15.5, moving 49"/min, Distance from Earth 0.8 LD<br />
Stack of 77 x 4 second exposures, 01:31:30 - 01:45:56 UT 29 May 2012<br />
0.40-m Schmidt-Cassegrain at f/6, 2.1"/pixel, field 9.4'x7.7', North up.</td></tr>
</tbody></table>
Even though it was nearly 19 hours after discovery it had only moved about 3° from the discovery position, still headed almost straight at us, but had approached to just 0.76 LD by then. Mt. Lemmon remarkably managed to keep it under observation to within an hour of closest approach, their last reported astrometry was at 06:17 UT when 2012 KT42 would have been about 12th mag and just 3.6 Earth diameters above the Earth's surface, screaming along at 1,630"/min, equivalent to the apparent diameter of the moon in less than 70 seconds!<br />
<br />
The alignment of 2012 KT42 during this approach was quite interesting, as already mentioned, it was nearly at the opposition point during most of the approach, but was actually in the Earth's penumbra from about 14:10 to 21:40 UT on May 28th. After close approach the line-up was still perfect and 2012 KT42 was in transit in front of the Sun for about an hour either side of 10:12 UT on May 29th, though far too small at about 0.006" diameter to be visible from Earth.Peter Birtwhistlehttp://www.blogger.com/profile/13429846157607762259noreply@blogger.com1tag:blogger.com,1999:blog-3211073665353586708.post-19252733122601376352012-06-06T19:14:00.000+01:002012-06-06T19:14:38.606+01:00Understanding the MPC's discovery credit rulesIn last month's Planetary notes in the April 2012 <a href="http://www.theastronomer.org/" rel="nofollow" target="_blank">The Astronomer</a> magazine (TA Vol 48 No 576 p327 [2012]) sub-editor Mark Kidger commented that I had discovered 3 Main Belt asteroids during March but that's not quite true(!) so it gives me an opportunity to try and explain the Minor Planet Center's (MPC) new rules relating to assigning minor planet discovery credit, published in an editorial notice in <a href="http://www.minorplanetcenter.net/mpec/K10/K10U20.html" rel="nofollow" target="_blank">MPEC 2010-U20</a> on 2010 Oct. 19th.<br />
<br />
In my astrometry report submitted to Mark I had indicated that minor planets 2012 FU<sub>1</sub>, 2012 FW<sub>1</sub> and 2012 FX<sub>1</sub> were Great Shefford "designations", rather than discoveries. These three objects, along with two others had been picked up on the night of March 17/18th, on images exposed for three <a href="http://www.minorplanetcenter.net/iau/NEO/ToConfirm.html" rel="nofollow" target="_blank">NEO Confirmation Page</a> objects. As a standard practice I check for any other moving objects in the field of view and if any are found, use the "Known Object Overlay" tool of <a href="http://www.astrometrica.at/" rel="nofollow" target="_blank">Astrometrica</a> to identify them, then measure positions and send in astrometry to the MPC. However, none of the five objects could be matched with known objects and a subsequent check against the MPC's <a href="http://scully.cfa.harvard.edu/cgi-bin/checkmp.cgi" rel="nofollow" target="_blank">Minor Planet Checker</a> also did not come up with any exact matches.<br />
<br />
Positions for all five objects were measured and, as they had not been identified with known objects I gave them my own observer-assigned temporary designations of GSC3HA - GSC3HE and immediately sent the astrometry in to the MPC. Four minutes later an automated message was received back identifying GSC3HB with main-belt minor planet 2006 BQ<sub>34</sub>, but nothing was received back for the other four objects.<br />
<br />
The next night was clear and along with other NEO work, follow-up images were taken for the remaining four objects and positions measured. For each object the positions from the previous night were then combined with the newly measured positions and new observer-assigned temporary designations given to each object. The astrometry for the two nights for each object were then sent off to the MPC. So for instance, from the first night, three positions were sent in for object GSC3HA, on the second night another three positions were obtained for the same object and all 6 positions were sent to the MPC with new observer-assigned temporary designation of GSC3JA.<br />
<br />
By sending in observations from just a single night the MPC's automated linking routines might have a hard task to match those positions with other observations of potentially the same object that might have been made many days or even weeks earlier. Submitting two nights at the same time, with the same ID used for both nights gives the matching routines a head start to locate other relatively recent observations. As soon as the matching routines put more than one night of observations together and don't match with any known object then they will automatically allocate a new MPC provisional designation and this is what happened for the four remaining objects, receiving provisional designations 2012 FT<sub>1</sub>, 2012 FU<sub>1</sub>, 2012 FW<sub>1</sub> and 2012 FX<sub>1</sub>.<br />
<br />
This would have been the first step towards achieving discovery credit if following the MPC rules prior to
2010 Oct. 19th - if further observations allowed identification to an earlier apparition for the object where a good orbit had been determined then that earlier apparition would take precedence, but otherwise, the observations that had allowed the provisional designation to be assigned would eventually lead (when the orbit was determined well enough to be numbered) to that observer being given discovery credit and the right to name the minor planet.<br />
<br />
However, with the new rules there is nothing special about the assigning of a provisional designation such as 2012 FT<sub>1</sub>. Every single observation needs to be associated with a designation and if it appears that an object cannot immediately be identified with a known designation then a new one is automatically assigned by the MPC. In this way it is quite possible that the same object gets more than one provisional designation during a single opposition and very likely, if it has been observed at earlier oppositions it will have received one or more provisional designations from those earlier apparitions in the process too. <br />
<br />
As the orbit gets more and more refined (as new observations are made, or older observations are identified from previous oppositions), eventually the orbital uncertainties are determined to be so small that the object is ready for permanent numbering by the MPC. It is only at this point that discovery credit is assigned. Central to this assignment is a new MPC procedure, introduced with the new rules on 19th Oct. 2010 that stores the date & time that the MPC <b><i>received</i></b> the astrometry from the observer, along with the more familiar details of Observatory code, date & time of observation, RA and Dec etc. These dates & times of receipt are called timetags by the MPC. Observations sent in before the new rules came into play have timetags constructed that are "<i>related to the date of observation</i>". Unfortunately, there is currently no means for an observer to see the timetags associated with observations that have been sent in to the MPC.<br />
<br />
The MPC rules state in MPEC 2010-U20 :<br />
<br />
"<i>Discoverers will be defined only when an object is numbered. At that time, the timetags on all the observations included in the solution will be examined. The discovery observation will be that observation which is the earliest-reported observations at the opposition with the earliest-reported second-night observation. The discovery observation will then define the discoverer.</i>"<br />
<br />
and <br />
<br />
"<i>Objects that have multiple-opposition orbits as of now (2010 Oct. 19) will be grandfathered into the old scheme of assigning discovery credit</i>"<br />
<br />
There are several points to note in these statements:<br />
a) For discovery credit to be assigned there must be at least two nights of positions reported, no assignment is possible where only a single night is available during an opposition. <br />
<br />
b) The early reporting of astrometry matters. If an observer detects a new object on night 1 and sends in his astrometry on night 3, but in the meantime, another observer detects the same object on night 2 and sends his astrometry in immediately, then the second observer would be selected for discovery credit in preference to the first because the night 2 astrometry would have been received by the MPC first.<br />
<br />
c) By the time an object is numbered it will quite likely have been observed on at least 3 oppositions, but the discovery credit will be assigned to the opposition that has the earliest-<b><i>reported</i></b> second-night observation, not necessarily the earliest opposition. So for example, if old NEAT images from 2003 are mined for moving objects and positions measured and submitted today for an object on several nearby nights back in 2003 they might end up being the only observations from the chronologically earliest observed opposition, but would have been reported last and therefore would not be considered for discovery credit. <br />
<br />
d) An object observed at more than one opposition before the new rules came into effect will have the previous rules applied and therefore discovery credit is likely to go to observations from one of those old oppositions. An object observed at only one opposition before the new rules will have the new rules applied (but with timetags for the old observations based on the date of observation, not date submitted) so credit is also likely to go to observations made at the old opposition.<br />
<br />
So, returning to the four objects I observed on March 17th that had received provisional designations, at the time of writing (6th June 2012):<br />
<br />
2012 FT<sub>1</sub>: Now identified with observations on 3 nights in 2005 obtained by Spacewatch (code 691) and Moletai Astronomical Observatory in Lithuania (code 152) so discovery credit is likely to go to one of those observatories.<br />
<br />
2012 FU<sub>1</sub>: Observations from Spacewatch (code 691) on March 16 and Mt Lemmon (code G96) on March 17 pre-date my positions from March 17th and very likely 691 and G96 submitted their observations in near-real time, so if no earlier observations are uncovered, discovery credit is likely to go to either 691 or G96, depending on which submitted first.<br />
<br />
2012 FW<sub>1</sub>: Observations from Pan-STARRS (code F51) on Feb. 27 and Mt Lemmon (code G96) on March 13 pre-date my positions from March 18th and again, F51 and G96 are likely to have submitted their observations in near-real time, so if no earlier observations are uncovered discovery credit is likely to go to F51.<br />
<br />
2012 FX<sub>1</sub>: Observations from Pan-STARRS (code F51) on March 16.5UT pre-date my positions from March 18.11UT and again, F51 probably submitted their observations in near-real time, so if no earlier observations are uncovered discovery credit is likely to go to F51.<br />
<br />
Without being able to examine the timetags for 2012 FU<sub>1</sub> and especially 2012 FX<sub>1</sub>, it can't be completely ruled out that my positions were in fact the first submitted, even though it is very, very unlikely! Additionally, as mentioned earlier, discovery credit is only assigned when the objects are finally numbered and therefore these guesses at how the credit will be assigned may all change if still unidentified observations that have been reported possibly years earlier are linked as further observations accumulate in upcoming oppositions. So I am fully expecting that all of those four objects will be assigned to other observatories by the time they each get permanent numberings.<br />
<br />
So my advice to observers wanting to try and get discovery credit for moving objects they find in their images is:<br />
<br />
- Measure and report unidentified objects as soon as possible, preferably on the same night as the exposures are obtained<br />
<br />
- Try to get at least a second night of astrometry and preferably a third, just in case no other positions have been reported from anywhere else this opposition<br />
<br />
- Assume the worst, it is very rare now that an object will be found without any earlier 2 or more night oppositions and very difficult to find an object that has not already been picked up and reported by one of the big surveys earlier in the same opposition. Difficult but not impossible.<br />
<br />
- Don't hold your breath! Even if you have a promising candidate, it could be some years before you know whether your observations will definitely receive discovery credit or not.<br />
<br />
[This post has minor updates from the originally published article that appeared in the May 2012 <b>The Astronomer</b> magazine (TA Vol 48 No 577 p19-21 [2012])]Peter Birtwhistlehttp://www.blogger.com/profile/13429846157607762259noreply@blogger.com7tag:blogger.com,1999:blog-3211073665353586708.post-50253423507864540142012-05-10T23:11:00.000+01:002012-05-15T02:48:10.154+01:00NEO 2008 PG1 recoveredEarlier today the Minor Planet Center (MPC) published circulars for four Near-Earth asteroids, each one having already received a designation two or more years ago. In each case the MPC had managed to link old positions with newer ones that had until now managed to evade detection as referring to the same object. These new linkages allowed each of their orbits to be substantially improved:<br />
<br />
<a href="http://www.minorplanetcenter.net/mpec/K12/K12J26.html" rel="nofollow" target="_blank">MPEC 2012-J26</a> 1999 OQ3 (2012 Apr positions linked to 1999 Jul-Oct positions)<br />
<a href="http://www.minorplanetcenter.net/mpec/K12/K12J27.html" rel="nofollow" target="_blank">MPEC 2012-J27</a> 2012 FB57 = 2008 VO12 (2012 Mar-Apr positions linked to 2008 Nov positions)<br />
<a href="http://www.minorplanetcenter.net/mpec/K12/K12J28.html" rel="nofollow" target="_blank">MPEC 2012-J28</a> 2010 VZ71 = 2010 MB113 (2010 Nov-2011 Jan positions linked to 2010 Jun positions)<br />
<a href="http://www.minorplanetcenter.net/mpec/K12/K12J29.html" rel="nofollow" target="_blank">MPEC 2012-J29</a> 2009 EV = 2008 PG1 (2009 Mar positions linked to 2008 Aug positions)<br />
<div>
<br /></div>
It looks like the MPC may have recently introduced some enhanced routines to search for linkages in their archive of old observations, the positions linking 2009 EV with 2008 PG1 for instance have been available for three years and only now has the connection been made that they are the same object.<br />
<br />
2008 PG1 was only observed on two nights in August 2008, discovered by LINEAR on August 3 and observed 16 hours later from Great Shefford on the morning of Aug 4th, the discovery was announced the same day in MPEC <a href="http://www.minorplanetcenter.net/mpec/K08/K08P14.html" rel="nofollow" target="_blank">2008-P14</a>. Attempts were made from Great Shefford to recover it on the next two clear nights but without success and it was the subject of a note here in <a href="http://peter-j95.blogspot.co.uk/2008/09/2008-august-notes-observing-statistics.html#2008PG1" target="_blank">September 2008</a>. With a very uncertain orbit it was listed by JPL as a Virtual Impactor with the first (very low probability) impact with Earth predicted to happen as early as 2013.<br />
<br />
Update 15 May 2012: Following the linkage and subsequent orbital improvement, the JPL Sentry system has been able to remove 2009 = 2008 PG1 from their list of <a href="http://neo.jpl.nasa.gov/risk/index_d.html" target="_blank">potential future Earth impact events</a>.<br />
<br />
Following the linkage of 2009 EV to 2008 PG1 by the MPC, the images taken at Great Shefford on the mornings of 2008 Aug. 9th and 13th were re-examined to check whether 2008 PG1 would have been in the field of view during those search attempts. On Aug. 9th, four fields were taken, spanning 1° but further searching had to be abandoned because of the approaching dawn. Unfortunately, just one more field would have picked it up, close but not close enough. With a rapidly expanding uncertainty area, fields taken on the morning of Aug 13th were all more than 2.5° away from the actual position.Peter Birtwhistlehttp://www.blogger.com/profile/13429846157607762259noreply@blogger.com0tag:blogger.com,1999:blog-3211073665353586708.post-39099945754933113142012-04-10T10:44:00.000+01:002012-05-17T20:50:50.189+01:00A rush of NEOs near Earth<br />
Rather unusually, two newly discovered near-earth asteroids were observed as bright as 13th magnitude during March. The first to be discovered was 2012 EG5, by the 1.8-m Pan-STARRS telescope on March 13th. It was only 21st magnitude at that time and still 19 days away from closest approach. Many observers reported it brightening steadily on its way in and several posted on the Minor Planet Mailing List (MPML) forum that they had measured it to have a 17.5 minute rotation period, with an amplitude of about 1/3 mag. My last observation, at 23:05 UT on March 31, found it at 13th mag and rushing south at 155"/minute, already at a declination of -25° and altitude of only 11°. It was just 5,000 miles outside of 1 Lunar Distance (LD) from Earth and would reach a minimum distance of 0.6 LD about 10 hours later but at a declination of about -55°. On the MPML, Dr Lance Benner mentioned some days later that although they had expected to be successful, his team using the Goldstone RADAR had failed to record echoes from 2012 EG5, indicating that it might be significantly smaller and/or less reflective than they had thought, based on an assumed diameter of ~50 metres, derived from its absolute magnitude.<br />
<br />
The second 13th mag NEO was 2012 FP35. It was discovered by the Catalina Sky Survey with their 0.68-m Schmidt on March 24 at 06:12 UT and in contrast to 2012 EG5 it was just 48 hours from closest approach. By the evening of March 24th in the UK it was still listed as unconfirmed on the NEO Confirmation Page, with an indicated uncertainty in position of about 1/4°. I searched for it but didn't find it in the uncertainty area, finally picking it up about 1/2° away from its predicted place. It was at about 4 LD by then, 18th mag and moving at about 11"/min against the sky. Just 21 hours later the following night, when first picked up at 20:12 UT it was moving about ten times faster at 103"/min and was about 2.5 magnitudes brighter and passed inside 1 LD at about 23:00 UT. I followed it into morning twilight and last registered it at 04:53 UT on March 26 by which time it had approached to 0.44 LD and was screaming along at just over 1,000"/min. At that speed I was limiting my exposures to just 0.2 seconds to reduce image trailing and could only get a batch of 5 images exposed before 2012 FP35 had travelled from one side of my field of view to the other, necessitating frequent telescope repositioning.<br />
<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://www.birtwhistle.org/images/PBirtwhistle_2012FP35_20120326_0449_0.2_2x2.gif" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" src="http://www.birtwhistle.org/images/PBirtwhistle_2012FP35_20120326_0449_0.2_2x2.gif" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">NEO 2012 FP35 on 2012 March 26 04:49:08 - 04:49:38 UT, 5 exposures of 0.2 second duration, each separated by 7 seconds. Motion 1,000"/min, mag +14. Distance from Earth 0.44 Lunar Distances.<br />
Galaxy NGC 4026 is to centre-left, magnitude +11.5.</td></tr>
</tbody></table>
<br />
<br />
Even though 2012 FP35 was at 13th magnitude and could be easily seen on the individual images, most of the fields taken could not be measured because of a lack of comparison stars bright enough to register due to the very short exposures. 2012 FP35 was intrinsically about 3.5 magnitudes fainter than 2012 EG5, indicating a diameter of only 7-10 metres.<br />
<br />
Coincidentally, on the same night another recently discovered NEO, 2012 FS35 was also under observation and also within 1 LD at the same time as 2012 FP35. I last observed 2012 FS35 on March 26 at 02:21 UT as a 17th mag object moving at 90"/min. It was at a distance of 0.57 LD by then but would approach to just 0.17 LD or about 4.5 Earth diameters from the Earth's surface about 15 hours later. However, 2012 FS35 is much smaller than even 2012 FP35, with an estimated diameter of only 2-3 metres so would not have posed any appreciable risk even if it had come closer and impacted the Earth.Peter Birtwhistlehttp://www.blogger.com/profile/13429846157607762259noreply@blogger.com0tag:blogger.com,1999:blog-3211073665353586708.post-4876372770409962632012-03-10T01:10:00.015+00:002012-05-05T11:47:17.461+01:00Finding needles in haystacks, minor planet styleEarly in February the Minor Planet Center's (MPC) <a href="http://www.minorplanetcenter.net/iau/NEO/BrightRecovery.html" rel="nofollow" target="_blank">Bright Recovery Opportunities</a> page was listing NEO 2006 AL8 as a bright, well placed but fast moving evening target, ideal for a recovery attempt.<br />
<br />
It had been discovered on 08 Jan 2006 by Gordon Garradd and Rob McNaught from Siding Spring and then followed for 7 weeks. With a period of 6 years, this was its first return to the Sun since discovery and unfortunately the 3-sigma uncertainty in the predicted ephemeris position by 02 Feb 2012 covered a massive 54° of sky, 33° to the east of the nominal position and 21° to the west. However it was also predicted to be 16th mag. and moving at about 27"/min, so if it could be caught in the telescope field of view it ought to be a very noticeable moving object. The Moon was due to be full on Feb. 8th and so many fainter NEO targets were already getting blotted out by the strengthening moonlight, searching for 2006 AL8 seemed like a good way to use an otherwise not particularly useful sky.<br />
<br />
First step in the search was to retrieve all the existing astrometry for the NEO via the MPC's <a href="http://www.minorplanetcenter.net/db_search" rel="nofollow" target="_blank">MPC Database</a> option, one of the standard options on the left of most of the MPC's web pages. This astrometry was then pasted into Bill Gray's <a href="http://www.projectpluto.com/find_orb.htm" rel="nofollow" target="_blank">Find_Orb</a> orbit determination program to generate an orbit and have a look at the residuals from the original astrometry. One of the functions of the program allows the filtering out of any astrometry with residuals larger than a set maximum and this was done over a series of steps, starting with a fairly generous limit of 2 arc-seconds, then gradually reducing to a harsh 0.75 arc-seconds, causing a number of the positions to be ignored in the orbit determination. Care has to be taken here, the intention is to only remove positions with large random errors and pushing the limit too small can start to drop good positions and degrade the quality of the solution.<br />
<br />
The resulting orbit was then used to generate an ephemeris for the current night and this was compared with the MPC's nominal prediction which was generated from an orbit which only excluded positions with residuals in excess of about 2 arc-seconds. The Find_Orb prediction placed 2006 AL8 to the east of the MPC prediction, but only a couple of degrees from the MPC place. A few other orbits with some different selections of positions were calculated and all placed the NEO to the east of the MPC position, with relatively little scatter.<br />
<br />
At 18:28 UT on 02 Feb I started my search at the MPC nominal position and then used the hint from Find_Orb to move east along the line of variation, taking 21 x 4 second exposures of each overlapping field. As each set of images was being exposed they were blinked using <a href="http://www.astrometrica.at/" rel="nofollow" target="_blank">Astrometrica</a>, looking for the moving object and in the 6th field 2006 AL8 was glaringly obvious, moving west to east at mag +16.3R, 1.2° from nominal.<br />
<div class="separator" style="clear: both; text-align: center;">
<br /></div>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://www.birtwhistle.org/images/PBIrtwhistle_2006AL8_20120202_1853-1857UT.gif" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img alt="NEO 2006 AL8 recovery field on 2012 Feb 02" border="0" src="http://www.birtwhistle.org/images/PBIrtwhistle_2006AL8_20120202_1853-1857UT.gif" title="NEO 2006 AL8 recovery field on 2012 Feb 02" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><span style="font-size: small;">NEO 2006 AL8 can be seen to the lower right, moving right to left in this video made from 21 images, each frame a 4 second exposure.</span></td></tr>
</tbody></table>
<br />
It had only taken 25 minutes from taking the first image to recover it. Another set of images was obtained the next night and the two nights of astrometry were sent off to the MPC at 18:40 UT on 03 Feb. Within the hour the MPC published <a href="http://www.minorplanetcenter.net/mpec/K12/K12C17.html" rel="nofollow" target="_blank">MPEC 2012-C17</a> announcing the recovery.<br />
<br />
Large uncertainties like the 54° in this case need not be quite as daunting as they might initially seem. If the object is bright enough to be seen in individual images and careful handling of the available astrometry is done, in the majority of cases the correct side of an uncertainty area can be chosen, halving the potential search and often also helping to give a reasonable clue to the whereabouts within the remaining uncertainty area. The same process often helps with newly discovered NEOs on the <a href="http://www.minorplanetcenter.net/iau/NEO/ToConfirmRA.html" rel="nofollow" target="_blank">NEO Confirmation page</a> when uncertainties are large, though often this is made more difficult when there are just a handful of positions for a new object, making it impossible to decide which positions are more in error than others, compared with the recovery of an existing object where there may be dozens or even hundreds of positions available.<br />
<br />
<div>
<br /></div>Peter Birtwhistlehttp://www.blogger.com/profile/13429846157607762259noreply@blogger.com0tag:blogger.com,1999:blog-3211073665353586708.post-3964240414159437782011-12-19T00:59:00.001+00:002011-12-19T01:02:12.829+00:00Confirming the recovery of Comet P/2006 T1 (Levy)<div class="separator" style="clear: both; text-align: center;"></div><div style="text-align: left;">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.<br />
<br />
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.</div><div style="text-align: left;"><br />
</div><div style="text-align: left;">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).</div><div style="text-align: left;"><br />
</div><div style="text-align: left;">Images taken from Great Shefford Observatory of the comet at its 2006 discovery apparition can be found <a href="http://www.birtwhistle.org/GalleryC2006T1.htm" target="_blank">here</a>.<br />
<br />
</div><div class="separator" style="clear: both; text-align: center;"><br />
</div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgnDzZ1_j5Q_cPIUW1HZpe6JzSIriYNPqk2GGv9j3fKvjCux5STuIeTIyp_e11jLCoCIV0893Dhp-4lW7UrObgUvlo7q1BTiwdTQrJWbvhP4dYe_ueYHguoFYR6o-odYzBrLOVBAAK_oAwd/s1600/PBirtwhistle_P2006T1_20111217.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgnDzZ1_j5Q_cPIUW1HZpe6JzSIriYNPqk2GGv9j3fKvjCux5STuIeTIyp_e11jLCoCIV0893Dhp-4lW7UrObgUvlo7q1BTiwdTQrJWbvhP4dYe_ueYHguoFYR6o-odYzBrLOVBAAK_oAwd/s1600/PBirtwhistle_P2006T1_20111217.jpg" /></a></div>Peter Birtwhistlehttp://www.blogger.com/profile/13429846157607762259noreply@blogger.com0tag:blogger.com,1999:blog-3211073665353586708.post-62474621941671229932011-12-09T00:04:00.007+00:002012-05-19T15:20:32.694+01:002011 November notesPoor 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.<br />
<br />
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.<br />
<br />
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.<br />
<br />
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 (<a eudora="autourl" href="http://minorplanetcenter.net/NEOCPblog/">http://minorplanetcenter.net/NEOCPblog/</a>) 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.<br />
<br />
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 <a href="http://www.minorplanetcenter.net/mpec/K11/K11W18.html" target="_blank">MPEC 2011-W18</a>, 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!<br />
<br />
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 <a eudora="autourl" href="http://ssd.jpl.nasa.gov/horizons.cgi">http://ssd.jpl.nasa.gov/horizons.cgi</a> 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.Peter Birtwhistlehttp://www.blogger.com/profile/13429846157607762259noreply@blogger.com0tag:blogger.com,1999:blog-3211073665353586708.post-85035670768874689352011-10-05T21:00:00.013+01:002011-12-20T20:35:19.210+00:002011 September notesA 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. <br />
<br />
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. <br />
<br />
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.<br />
<br />
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.<br />
<br />
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.<br />
<br />
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<span style="font-size: xx-small;">,</span> 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.<br />
<br />
Here 2011 SE58 is seen passing from west to east through the 18'x18' field of view in less than 2 minutes<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjlp1oHrjqOcym4bYZVnHvyc3AXnqwGXaTijUnv_KdRUQVJNtYQsk6pzBfy3cdX-tUACA35DibWBvbGm1en2Rl2vsMGulDuPcV1wp5e8nKxTNjzv4KupRzpDRjGOgSN2d0KY8aQuJDjIkwQ/s1600/2011SE58_20110926_234301-234451-50.gif" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjlp1oHrjqOcym4bYZVnHvyc3AXnqwGXaTijUnv_KdRUQVJNtYQsk6pzBfy3cdX-tUACA35DibWBvbGm1en2Rl2vsMGulDuPcV1wp5e8nKxTNjzv4KupRzpDRjGOgSN2d0KY8aQuJDjIkwQ/s1600/2011SE58_20110926_234301-234451-50.gif" /></a></div><br />
<br />
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!Peter Birtwhistlehttp://www.blogger.com/profile/13429846157607762259noreply@blogger.com0tag:blogger.com,1999:blog-3211073665353586708.post-52096026863242387412011-09-09T03:08:00.001+01:002011-09-09T03:12:50.813+01:002011 August notes: An amateur discovered tumbling NEOAugust 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.<br />
<br />
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 <a href="http://www.minorplanets.org/OLS/index.html" target="_blank">La Sagra Sky Survey</a> 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.<br />
<br />
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.<br />
<br />
<a href="http://www.minorplanetobserver.com/MPOSoftware/MPOCanopus.htm" target="_blank">Canopus</a> 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.<br />
<br />
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.<br />
<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgK2BP_TccV6-_fW8slXTdlQyW3Np0A1b4D2goKt7gS8J1gqu0sEurHByte53TK14vMgiasoyiQrQToxc8lI8jUe5kHKq_gdCpvO1TWnypmf6tIvXKgTVv_C55q_FvEpljSat1eePOxmLXj/s1600/2011_PE2-Raw.png" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="325" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgK2BP_TccV6-_fW8slXTdlQyW3Np0A1b4D2goKt7gS8J1gqu0sEurHByte53TK14vMgiasoyiQrQToxc8lI8jUe5kHKq_gdCpvO1TWnypmf6tIvXKgTVv_C55q_FvEpljSat1eePOxmLXj/s400/2011_PE2-Raw.png" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Raw (unfolded) lightcurve of 2011 PE2 from 348 data points obtained 2011 Aug. 09 00:14-03:08 UT</td></tr>
</tbody></table>Peter Birtwhistlehttp://www.blogger.com/profile/13429846157607762259noreply@blogger.com0tag:blogger.com,1999:blog-3211073665353586708.post-41687719172429501302011-08-28T00:03:00.022+01:002011-08-28T01:28:59.775+01:00Bright Supernova 2011fe in galaxy M101Discovered automatically by the The <a href="http://www.astro.caltech.edu/ptf/">Palomar Transient Factory</a> 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.<br />
<br />
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.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhTt-ELYg9aLYt5k5FxNu40_tSCq0sCFDtBLsgbSV2gY90M-brEWDJVtu_MlyDK-fB7BlrdJDLE0JVM1G2sCvtPkHpMIV0D3_y2PnmUcsIR0ZbsWT4ROkYbFtwgO3Nivf1LIN-MwMgvOBOc/s1600/M101-2011fe-20110827.gif" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhTt-ELYg9aLYt5k5FxNu40_tSCq0sCFDtBLsgbSV2gY90M-brEWDJVtu_MlyDK-fB7BlrdJDLE0JVM1G2sCvtPkHpMIV0D3_y2PnmUcsIR0ZbsWT4ROkYbFtwgO3Nivf1LIN-MwMgvOBOc/s1600/M101-2011fe-20110827.gif" /></a></div><br />
<div class="separator" style="clear: both; text-align: center;"></div><div class="separator" style="clear: both; text-align: center;"></div>Peter Birtwhistlehttp://www.blogger.com/profile/13429846157607762259noreply@blogger.com0tag:blogger.com,1999:blog-3211073665353586708.post-45090307825009156952011-08-19T03:03:00.002+01:002011-08-19T07:13:33.825+01:00The Sky At Night comes to Great SheffordThe 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 <a href="http://peter-j95.blogspot.com/2011_06_01_archive.html">June</a> and <a href="http://peter-j95.blogspot.com/2011/08/2011-july-notes-2011-md-and-2000-cp101.html">July</a> notes).<br />
<br />
The interview was included in the program "Dawn at Vesta" and was first transmitted in the early hours of Monday 8th August on BBC1.<br />
<div class="separator" style="clear: both; text-align: center;"></div><br />
Watch the interview with Paul Abel here:<br />
<br />
<div class="separator" style="clear: both; text-align: center;"><iframe allowfullscreen='allowfullscreen' webkitallowfullscreen='webkitallowfullscreen' mozallowfullscreen='mozallowfullscreen' width='320' height='266' src='https://www.youtube.com/embed/qHxV7bdMhrQ?feature=player_embedded' frameborder='0'></iframe></div>Peter Birtwhistlehttp://www.blogger.com/profile/13429846157607762259noreply@blogger.com1tag:blogger.com,1999:blog-3211073665353586708.post-15373964900003112192011-08-09T01:48:00.006+01:002011-08-13T22:21:56.804+01:002011 July notes: 2011 MD and recovering 2000 CP101Early 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 <u>and</u> 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 <a href="http://neo.jpl.nasa.gov/news/news172.html">here</a>)<br />
<br />
<div>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.</div><div></div><div>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.</div><br />
<div>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.</div><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhUd0NPuGIQZJs00epGMUELVfAvdIt84nGRYcNtiJfy4AFRurDn_uDY2dQBkLIN5o4WZRlohMWhk7ED-AyjxPvnRS3Bwdmz5WjHkc8mXwK4uVQwUOX2QBUtkkZBNVAPUc49-LwOoRJHgNJ1/s1600/2011MD-20110702-Path2.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhUd0NPuGIQZJs00epGMUELVfAvdIt84nGRYcNtiJfy4AFRurDn_uDY2dQBkLIN5o4WZRlohMWhk7ED-AyjxPvnRS3Bwdmz5WjHkc8mXwK4uVQwUOX2QBUtkkZBNVAPUc49-LwOoRJHgNJ1/s1600/2011MD-20110702-Path2.JPG" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Track of 2011 MD on 2011 July 3.07 UT, 9'x9' field of view</td></tr>
</tbody></table><div></div><div>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.</div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgfman_xMFisPPMaR7V0biiu57VV1YgibkHy5cveq_REeszAbty_TP1CBHLdRypRjgJljqrhwHtP6iOyWQEtqxoK_k1gCVDbUw8_WPELza5M8uM8AUPUbHj1J9rV6gKceDEILLpD9B4mdTY/s1600/2011MD_20110703_013934_20_2x2_139%252B31-Annotate.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" naa="true" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgfman_xMFisPPMaR7V0biiu57VV1YgibkHy5cveq_REeszAbty_TP1CBHLdRypRjgJljqrhwHtP6iOyWQEtqxoK_k1gCVDbUw8_WPELza5M8uM8AUPUbHj1J9rV6gKceDEILLpD9B4mdTY/s1600/2011MD_20110703_013934_20_2x2_139%252B31-Annotate.jpg" /></a></div><div><br />
</div><div>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.</div><br />
<div>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 <a href="http://www.minorplanetcenter.net/db_search">http://www.minorplanetcenter.net/db_search</a> 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.</div><div></div><div>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 <a href="http://www.minorplanetcenter.net/mpec/K11/K11O29.html">MPEC 2011-O29</a>.<br />
<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjfmA-v-iLn5cLuCqo5TgzMdvkH6W32kTKtpsBDNnYcpp9yd4nXQFKlLZExFBoSJPuhhGYi8N6DuW1rHXzzDNI2voQNkzfuZWt3_4X2nahbbjGmuwhNY3uDIAZ9uksTtCQl_Cj52fKopWth/s1600/SkyMap20110723a.png" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="306" naa="true" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjfmA-v-iLn5cLuCqo5TgzMdvkH6W32kTKtpsBDNnYcpp9yd4nXQFKlLZExFBoSJPuhhGYi8N6DuW1rHXzzDNI2voQNkzfuZWt3_4X2nahbbjGmuwhNY3uDIAZ9uksTtCQl_Cj52fKopWth/s400/SkyMap20110723a.png" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">The 13 fields taken during the search for 2000 CP101, Delphinus is at top left and Altair at lower right.<br />
Graphic generated using SkyMap Pro 9</td></tr>
</tbody></table> </div>Peter Birtwhistlehttp://www.blogger.com/profile/13429846157607762259noreply@blogger.com0tag:blogger.com,1999:blog-3211073665353586708.post-74877966949621254112011-06-28T01:46:00.004+01:002011-08-07T11:33:00.805+01:00Confirming the discovery of close approach asteroid 2011 MD<div class="separator" style="clear: both; text-align: center;"><br />
</div>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.<br />
<br />
The two new objects were posted on the NEOCP with the temporary designations assigned to them by the LINEAR team, BZ52584 and BZ52587. <br />
<br />
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).<br />
<br />
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.<br />
<br />
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!<br />
<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhCedMzoW4JHchJoWqWJm4iOtNdqMGfFnGQMnKmFJtfhQTfz60VChDotvNltJtXn78XAzTXDyWI-yNIFpwOVYEK8gh-jgmfIpAZGSv_HODRbHCDWGzsP6eWrronGHInEbQyK8cGoX6agH_l/s1600/BZ52584.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="178px" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhCedMzoW4JHchJoWqWJm4iOtNdqMGfFnGQMnKmFJtfhQTfz60VChDotvNltJtXn78XAzTXDyWI-yNIFpwOVYEK8gh-jgmfIpAZGSv_HODRbHCDWGzsP6eWrronGHInEbQyK8cGoX6agH_l/s320/BZ52584.jpg" width="320px" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">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</td></tr>
</tbody></table>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.<br />
<br />
All of the good images were then measured and positions sent off to the MPC at 02:05 UT. <br />
<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgUrRLZh1n-C2sxAKYTHiY2eKMz2vhcUxuj1CUzca9L2bEK62uZT9MOcmlmkWsvs1Nfr5EmqYR1s_9x2bG1acZ-5bL3tz6HzeUUxp5IdXL2_7FBeCfCNqSn7l__MWziKfAcbMuqggnGkM5v/s1600/BZ52584_20110623_PBirtwhistle341240.gif" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgUrRLZh1n-C2sxAKYTHiY2eKMz2vhcUxuj1CUzca9L2bEK62uZT9MOcmlmkWsvs1Nfr5EmqYR1s_9x2bG1acZ-5bL3tz6HzeUUxp5IdXL2_7FBeCfCNqSn7l__MWziKfAcbMuqggnGkM5v/s1600/BZ52584_20110623_PBirtwhistle341240.gif" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Animation of 2 sets of 5 x 20 second stacked exposures, showing motion of 2011 MD<br />
01:41-01:45 UT 23 June 2011</td></tr>
</tbody></table> <br />
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:<br />
<br />
<div style="text-align: center;"><em>"J95: BZ52584 probable v. close approach on June 27.2 UT"</em></div><div style="text-align: center;"><br />
<em>"FindOrb gives ~23,000Km on June 27.2 UT (leaving out 1 of 704 positions). Worth<br />
some more follow-up."</em></div><br />
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.Peter Birtwhistlehttp://www.blogger.com/profile/13429846157607762259noreply@blogger.com0tag:blogger.com,1999:blog-3211073665353586708.post-63855870616537711452011-05-08T18:23:00.003+01:002011-08-14T00:02:02.119+01:002011 April notes: 2011 GP59 and NEOCP changes<div style="border-bottom: medium none; border-left: medium none; border-right: medium none; border-top: medium none;">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.</div><div style="border-bottom: medium none; border-left: medium none; border-right: medium none; border-top: medium none;"><br />
</div><div style="border-bottom: medium none; border-left: medium none; border-right: medium none; border-top: medium none;">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.</div><div style="border-bottom: medium none; border-left: medium none; border-right: medium none; border-top: medium none;"><br />
</div> <table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="border-bottom: medium none; border-left: medium none; border-right: medium none; border-top: medium none; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgBkqGi2TBsVYL9hi1N5UmzDIyQdQaOZd8uzOhraPAJpgv6ANh4QY6jb3SKn95ozO3x4oLbZFerXjY9cnmfdKLEwptzD0YG8h2shpuE1K8-gSM59rqPdovjdW9VCwnfMqqou1oJtUkw1KZ8/s1600/2011_GP59-287-290.PNG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="240px" naa="true" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgBkqGi2TBsVYL9hi1N5UmzDIyQdQaOZd8uzOhraPAJpgv6ANh4QY6jb3SKn95ozO3x4oLbZFerXjY9cnmfdKLEwptzD0YG8h2shpuE1K8-gSM59rqPdovjdW9VCwnfMqqou1oJtUkw1KZ8/s320/2011_GP59-287-290.PNG" width="320px" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Initial lightcurve reduction, showing large scatter at the brightest part of the curve, where scatter would normally expected to be least</td></tr>
</tbody></table> <div style="border-bottom: medium none; border-left: medium none; border-right: medium none; border-top: medium none;">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.</div><div style="border-bottom: medium none; border-left: medium none; border-right: medium none; border-top: medium none;"><br />
</div> <table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEidElpHZ2tAhgDjlbVkl92HMKOvpCAwE7roihwx2Oq3S-9F8tl0i_ivjYbuxhPbHHTXRPPMyXpaKC7mldV28qP6LDww67kPWx-UpBCMIY5b7Vt1u2_vgFC0FRVJ2bNOcRBZ76n_BE_psP7A/s1600/2011_GP59-287-290-Period1.PNG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="240px" naa="true" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEidElpHZ2tAhgDjlbVkl92HMKOvpCAwE7roihwx2Oq3S-9F8tl0i_ivjYbuxhPbHHTXRPPMyXpaKC7mldV28qP6LDww67kPWx-UpBCMIY5b7Vt1u2_vgFC0FRVJ2bNOcRBZ76n_BE_psP7A/s320/2011_GP59-287-290-Period1.PNG" width="320px" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Primary lightcurve with secondary subtracted</td></tr>
</tbody></table> <div style="border-bottom: medium none; border-left: medium none; border-right: medium none; border-top: medium none;"><br />
</div><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiettH6nq_hchrxrpJFXFLJJKgY9o08_aihv00fiNwbuIYTu6nJBGGVS-qrRz8k1ZGecHtt-084suh-B8tfZjtKBXrHsvCyrV6A3Jgc8zju8qvhoZIq1dhfVcoHrCTbusQfV7Kik9i6CiCx/s1600/2011_GP59-287-290-Period2.PNG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="240px" naa="true" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiettH6nq_hchrxrpJFXFLJJKgY9o08_aihv00fiNwbuIYTu6nJBGGVS-qrRz8k1ZGecHtt-084suh-B8tfZjtKBXrHsvCyrV6A3Jgc8zju8qvhoZIq1dhfVcoHrCTbusQfV7Kik9i6CiCx/s320/2011_GP59-287-290-Period2.PNG" width="320px" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Secondary lightcurve with primary subtracted</td></tr>
</tbody></table><div style="border-bottom: medium none; border-left: medium none; border-right: medium none; border-top: medium none;">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 <a eudora="autourl" href="http://tech.groups.yahoo.com/group/mpml/message/25234">http://tech.groups.yahoo.com/group/mpml/message/25234</a> with periods of 7.3501 +/- 0.0004 minutes and 10.258 +/- 0.003 minutes.</div><div style="border-bottom: medium none; border-left: medium none; border-right: medium none; border-top: medium none;"><br />
</div><div class="separator" style="border-bottom: medium none; border-left: medium none; border-right: medium none; border-top: medium none; clear: both; text-align: center;"></div><div style="border-bottom: medium none; border-left: medium none; border-right: medium none; border-top: medium none;">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.</div><div style="border-bottom: medium none; border-left: medium none; border-right: medium none; border-top: medium none;"><br />
</div><div style="border-bottom: medium none; border-left: medium none; border-right: medium none; border-top: medium none;"><br />
</div><div style="border-bottom: medium none; border-left: medium none; border-right: medium none; border-top: medium none;">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.</div>Peter Birtwhistlehttp://www.blogger.com/profile/13429846157607762259noreply@blogger.com0tag:blogger.com,1999:blog-3211073665353586708.post-6325444993270322772011-04-10T23:30:00.004+01:002011-08-07T00:11:19.666+01:002011 March notes: 4 close approach NEOsFortunately 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.<br />
<br />
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.<br />
<br />
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.<br />
<br />
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.<br />
<br />
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.Peter Birtwhistlehttp://www.blogger.com/profile/13429846157607762259noreply@blogger.com0tag:blogger.com,1999:blog-3211073665353586708.post-47053829089668963202011-02-10T02:06:00.003+00:002011-08-15T00:39:46.474+01:00Visit to the Catalina Sky Survey<span style="font-family: Verdana;"></span>During the first week of February my job took me to <city w:st="on">Phoenix</city>, <state w:st="on">AZ</state> and before flying home, I took the opportunity to visit the Catalina Sky Survey (CSS) team in <city w:st="on"><place w:st="on">Tucson</place></city>. I met up with Principal Investigator Ed Beshore and co-P.I. Steve Larson at the Lunar and Planetary Laboratory within the <placetype w:st="on">University</placetype> of <placename w:st="on">Arizona</placename> 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 <city w:st="on"><place w:st="on">Tucson</place></city>.<br />
<br />
Later in the afternoon Ed drove me up the winding road to <place w:st="on"><placetype w:st="on">Mt.</placetype> <placename w:st="on">Lemmon</placename></place>, a 1.5 hour journey, initially crossing the Catalina foothills covered with magnificent Saguaro Cacti. Half way up the mountain, stunning views unfolded across <city w:st="on">Tucson</city>, to Kitt Peak 55 miles to the southwest and to <placetype w:st="on">Mt.</placetype> <placename w:st="on">Hopkins</placename> with the MMT 50 miles south, not surprising the area is dubbed "<place w:st="on"><placename w:st="on">Optical</placename> <placetype w:st="on">Valley</placetype></place>". 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.<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody></tbody></table><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgoV0dHuV5HUjhHSRrh_-VjedkVC3D3HVSexDjPJYkTuBIebUe1sA5elbmUr9OZVr2BVfgYiMmyHpAgyHLRmB_BWc4u9hIQsgqidQO0Rz47gOClxv7lpYaiGU2Wap7BHbUTemglLHKve-xk/s1600/CSS20110205MtGrahamW.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="136" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgoV0dHuV5HUjhHSRrh_-VjedkVC3D3HVSexDjPJYkTuBIebUe1sA5elbmUr9OZVr2BVfgYiMmyHpAgyHLRmB_BWc4u9hIQsgqidQO0Rz47gOClxv7lpYaiGU2Wap7BHbUTemglLHKve-xk/s400/CSS20110205MtGrahamW.jpg" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><span style="font-family: Verdana; font-size: 10pt;">The shadow of Mt. Lemmon pointing almost directly at the Large Binocular Telescope on Mt. Graham 50 miles away (top right in insert)</span></td></tr>
</tbody></table><br />
<div class="MsoNormal" style="margin: 0in 0in 0pt;"><span style="font-family: Verdana;">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.</span></div><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjLZ5UrT68514b2X0wTZzfvlrjN8399W2M2VcPmvtMta2WwYfrE9yXGX6AU_HxtkHHQAudquX_6-Rm-Z4qvvzx__tj5GmQuvVmxVoJBsl7Cictal3EECoKaf83ukwVWQGCi2Sx0xI2uzL3n/s1600/CSS20110205EdBeshoreAndG96W.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjLZ5UrT68514b2X0wTZzfvlrjN8399W2M2VcPmvtMta2WwYfrE9yXGX6AU_HxtkHHQAudquX_6-Rm-Z4qvvzx__tj5GmQuvVmxVoJBsl7Cictal3EECoKaf83ukwVWQGCi2Sx0xI2uzL3n/s400/CSS20110205EdBeshoreAndG96W.jpg" t$="true" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><div class="MsoNormal" style="margin: 0in 0in 0pt;"><span style="font-family: Verdana; font-size: 10pt;">Ed Beshore opens up the lower shutter of the <place w:st="on"><placetype w:st="on">Mt.</placetype> <placename w:st="on">Lemmon</placename></place> 1.5-m telescope</span></div></td></tr>
</tbody></table><div class="MsoNormal" style="margin: 0in 0in 0pt;"></div><div class="MsoNormal" style="margin: 0in 0in 0pt;"><span style="font-family: Verdana;">The observer for the night, Alex Gibbs arrived and continued preparing the telescope, running through focussing sequences and also choosing fields in the early evening sky ready for the survey work to start. Two computer flat screen monitors arranged side-by-side displayed the sky divided up into the fixed 1.2 x 1.2 field centres that are used night after night for all the survey work. Settings allowed the areas of sky that CSS and the other surveys such as LINEAR and Spacewatch had covered in recent nights to be colour-coded so that fresh unsurveyed sky could be targeted that evening.</span></div><br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg4y6gspcyX_hknVriYnMmYebmEXDRtnnwgZSKIFiQ4ojfHcJnuVhdTLO7MCGkWxGP7f7LprgKJzIFSbVjF1r8Io8lWHSkSjZnuHFWG24zOr5wSgUAVb0B-tqZ98eiG2QQsZKPIY0tLS65s/s1600/CSS20110205TwinMonitorsW.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="205" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg4y6gspcyX_hknVriYnMmYebmEXDRtnnwgZSKIFiQ4ojfHcJnuVhdTLO7MCGkWxGP7f7LprgKJzIFSbVjF1r8Io8lWHSkSjZnuHFWG24zOr5wSgUAVb0B-tqZ98eiG2QQsZKPIY0tLS65s/s400/CSS20110205TwinMonitorsW.jpg" t$="true" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><div class="MsoNormal" style="margin: 0in 0in 0pt;"><span style="font-family: Verdana; font-size: 10pt;">Field centres for the 1.5-m telescope, colour-coded showing where NEO surveying had been done in recent nights by other surveys</span></div></td></tr>
</tbody></table><br />
<div class="MsoNormal" style="margin: 0in 0in 0pt;"><span style="font-family: Verdana;">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.</span></div><div class="MsoNormal" style="margin: 0in 0in 0pt;"><span style="font-family: Verdana;"></span> <br />
<table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: left; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEghKQB-lUhTnj8U_ESic-MhMwHiimId8wsKuoxIr6cZytV_-BP1iBRQjX4oLKKFoMUNXwG1f6w9UHzewHU0bQkGtBNndChJIztJwemziV83gM-jhFomxd9yiZU7MPxJcubyJ_KIPvglxoTK/s1600/CSS20110205AlexGibbsW.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="275" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEghKQB-lUhTnj8U_ESic-MhMwHiimId8wsKuoxIr6cZytV_-BP1iBRQjX4oLKKFoMUNXwG1f6w9UHzewHU0bQkGtBNndChJIztJwemziV83gM-jhFomxd9yiZU7MPxJcubyJ_KIPvglxoTK/s400/CSS20110205AlexGibbsW.jpg" t$="true" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><span style="font-family: Verdana; font-size: 10pt;">Alex Gibbs selecting fields at the start of a night of NEO surveying by the 1.5-m Mt. Lemmon telescope</span></td></tr>
</tbody></table></div><div class="MsoNormal" style="border: currentColor; margin: 0in 0in 0pt;"><span style="font-family: Verdana;"></span><br />
<span style="font-family: Verdana;">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.</span></div><div class="MsoNormal" style="border: currentColor; margin: 0in 0in 0pt;"><br />
</div><div class="MsoNormal" style="border: currentColor; margin: 0in 0in 0pt;"><span style="font-family: Verdana;">With the 1.5-m telescope in full operation, Ed and I left to drive the 7 miles down to <placetype w:st="on">Mt.</placetype> <placename w:st="on">Bigalow</placename> where the CSS 0.68-m Schmidt is located (observatory code 703), 1000ft below the <place w:st="on"><placetype w:st="on">Mt.</placetype> <placename w:st="on">Lemmon</placename></place> 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 <place w:st="on">Mallorca</place> 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!</span></div><br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjATQjFkZAgPfByMdXTQZKwXlXtLdmAf2v4P7orTPysK45XzpoIP-_PDq8bQBcG7Dsetvbdy-IqH0xFcjZyTAXI7mKPqh0ICIvW7LATjT3d0kF2iCwaSOdCn8XUEeYgmL-nbOLdm2KLWQ9P/s1600/CSS20110205AndreaBoattiniW.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="287" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjATQjFkZAgPfByMdXTQZKwXlXtLdmAf2v4P7orTPysK45XzpoIP-_PDq8bQBcG7Dsetvbdy-IqH0xFcjZyTAXI7mKPqh0ICIvW7LATjT3d0kF2iCwaSOdCn8XUEeYgmL-nbOLdm2KLWQ9P/s400/CSS20110205AndreaBoattiniW.jpg" t$="true" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><span style="font-family: Verdana; font-size: 10pt;">Andrea Boattini blinking newly detected moving objects at the controls of the CSS 0.68-m Schmidt</span></td></tr>
</tbody></table><div class="MsoNormal" style="border: currentColor; margin: 0in 0in 0pt;"><span style="font-family: Verdana;">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...</span></div><br />
<div class="separator" style="border: currentColor; clear: both; text-align: center;"></div><br />
<div class="MsoNormal" style="margin: 0in 0in 0pt;"><br />
</div><div class="separator" style="clear: both; text-align: center;"></div><div class="separator" style="clear: both; text-align: center;"></div>Peter Birtwhistlehttp://www.blogger.com/profile/13429846157607762259noreply@blogger.com0tag:blogger.com,1999:blog-3211073665353586708.post-50571703057990454492011-01-06T01:34:00.004+00:002011-08-08T01:48:46.017+01:002010 XM56December 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!<br />
<br />
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<span style="font-family: Verdana;">°</span> increasing to 65<span style="font-family: Verdana;">°</span>) 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.<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjGx_3XZbQObnPaxSHw3cjFAyaWncJqZ8DjTL2cbswsd6zL7_cRE2f3xpf89Gl-b0F2TLPd4aDoKdooLGKEGM7mu8VWDBFkdLblzAPH0qpH0oUILUU6LYA68zVdtb8ktPQ9jfwZjFPWv28b/s1600/2010_XM56-Raw-ErrorBars.png" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="283px" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjGx_3XZbQObnPaxSHw3cjFAyaWncJqZ8DjTL2cbswsd6zL7_cRE2f3xpf89Gl-b0F2TLPd4aDoKdooLGKEGM7mu8VWDBFkdLblzAPH0qpH0oUILUU6LYA68zVdtb8ktPQ9jfwZjFPWv28b/s400/2010_XM56-Raw-ErrorBars.png" t$="true" width="400px" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Raw lightcurve of 2010 XM56 from 2010 Dec 16/17th</td></tr>
</tbody></table>Peter Birtwhistlehttp://www.blogger.com/profile/13429846157607762259noreply@blogger.com0