Tuesday 8 May 2007

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

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

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

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

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