Another good night for asteroids

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Another good night for asteroids

Unread post by Pete »

Thursday, 1 Dec 2011 It’s brisk and cold and clear today. While dinner’s cooking I’m generating an updated set of -30°C darks The moon’s high at 50% phase but there are 3 relatively bright asteroids selected from the MPC’s critical object list.

170502 (2003 WM7) is a 2.4km sized Apollo now 16 million miles from Earth and shining a relatively brilliant 14.8 magnitude. Uncertainty level is 1. Apparent motion is 10’/hr. I’d planned to catch this object at 18:00 but by the time I’ve synchronized the Meade 14”, focused it, and calibrated the AO guider it’s 18:20. No biggie. Imaged from 18:20 – 18:35 hrs., 30 second exposures, 2X2 binning, -30°C cooling, 10 Hz guiding. Frames 2, 8 & 15 show dRA = +0.4’ and dDEC = -0.7’. FWHM = 4.0 and S/N = 37, strong enough to nail down to the brightness to 15.1 ±0.1 magnitude.

42286 (2001 TN41) is a 3.5km sized Apollo now .8AU distant and 17.9 mag. Uncertainty level is 1 and motion is 1.555’/hr. Imaged from 18:45 – 19:16 hrs., as there was a second dimmer asteroid in the fov and I needed more photons as 42286 was processed. Imaged 2 min, 2X2, -30C, 3 Hz. The S/N on the asteroid in individual frames is so weak as to result in astrometry errors, so stacking was used. Frames 1-3, 4-6 & 7-9 show dRA = +0.1’ and dDEC = 0’.

130413 is not on the MPC list but is in the field of view. It’s an 4.6km sized main belt asteroid now 18.3 mag and 1.2AU distant and moving .52’/hr. Stacking, frames 1-4, 5-8 & 9-12 show dRA = +0.1’ and dDEC = 0’.

2011 WS74 is the night’s most exciting target. Discovered only 2 days ago, this 115 meter sized Aten is now 17.7 mag and just 3 million miles out. It’s ripping across the sky at 28’/hr. Uncertainty level is a high 7 out of 9, and orbital residual is a high .58 Imaged from 19:26 – 19:40 hrs at 10 sec, 2X2, -30C, 1Hz. Frames 1-10, 11-20 & 21-30 show dRA = +1.9’ and dDEC = +2.4’.

It’s down to freezing now and I’ve run the planned targets, but the sky’s wonderfully clear. Ducking into the house for 10 minutes results in a warm-up and two additional asteroids to chase.

2011 SL102 is 1.6km sized Amor now a bright 16.0 mag moving 2.2’/hr. It’s a circa 2001 asteroid that was lost and recently recovered. Uncertainty level is 1. Imaged from 20:09 – 20:22 hrs. at 1 min, 2X2, -30C, 1Hz. Frames 1, 4 & 8 show dRA = +0.3’ and dDEC = 0.

16834 (1997 WU22) is a 5.2km sized Apollo now 18.5 mag and 1.2AU distant. Movement is .75’/hr and uncertainty level is 1. Maybe I’m tired or cold but although image capture settings are recorded on the images I failed to note them on my working paper. Frames 1-3, 4-6 & 7-9 show dRA = +0.1 and dDEC = 0.

2000 RD55 is in the 16834 FOV. This 14.4km sized main belt asteroid is 1.8 AU distant and shining at 17.5 mag. Movement is only .27’/hr. Frames 1, 6 & 11 show dRA = +0.1’ and dDEC = -0.1’

That’s it for the night. I’m in by 21:15 and a total of 21 observations have been emailed to the MPC by 21:30. It was a great night. We’re coming into the transparency of winter.

hgp 17:10 hrs., 4 Dec 2011
Pete P.
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Re: Another good night for asteroids

Unread post by Rotorhead »

Nice job, Pete! And I agree that the most exciting find was the little guy with an uncertainty of 7. As I've said many times, you are doing real science, and it is fun to watch your progress right up into the big leagues, despite observing from your back yard and in a bright moon phase. It's not like you're observing from the top of some dark mountain somewhere... Old eyes or not, you are still doing some amazing astronomy. 21 observations in three hours (less a warm-up break :P ) sounds pretty darn impressive to me!
Bob M
15" f5 Starsplitter Dob/80mm Finder
5" Explore Scientific triplet APO on a Vixen Sphinx GEM
"He numbers all the stars, and calls each one by name." Ps 147:4