Astrometry plus 1st views of comet ISON

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Astrometry plus 1st views of comet ISON

Unread post by Pete » Thu Dec 20, 2012 11:10 am

Wednesday, 19 Dec 2012

Got home around 9:30 tonight and saw a cloudless transparent sky with a zillion stars. It’s been a long day but Comet ISON should be visible, and I’d promised Bill G that I’d check it out soonest. That’d be now.

I’m out at 22:07 and powered up and tracking in about ½ hour. There’s a 16th magnitude “star” where ISON should be when viewed thru 30 second exposures. Over 18 minutes the comet’s slow 28”/hour apparent motion leaves a short streak in the stacked processed final image.


C/2012 S1 ISON 22:55 EST Dec 19, 2012 N up, E left
Meade 14” LX200GPS @ f/5.87 SBIG ST-8XME @ 1min, 2X2 binning, -30C cooling
SBIG AO-8 guiding at 2 Hz 18 X 1 min

Seeing’s not all that good, and ISON’s still low in the east, but Photoshop cleans things up. The original reduced images used for astrometry showed brightness as 16.8, 16.7 and 17.0 magnitude, but the S/N was only around 13:1 so that kind of variation would be normal for such a weak signal.

2012 XF112 is a 723 meter sized Amor now 18.3 magnitude and .25 AU distant. Discovered 8 days ago, uncertainty level is 6. Apparent motion is 1.5’/hr. Imaged 23:26 – 00:10 hrs at 3 min, 2X2, -30C, 2 Hz. It’s passing through and in front of some stars so pulling out clean images takes more time than anticipated. Air temp’s 33°F. Seeing is much better now that I’m close to zenith and the longer 3 minute exposures are noise-free. Frames 1, 5 & 12 show dRA = +0.3’ and dDEC = +0.4’ Cloud’s moving in and the last frame is weak.

There’s cloud over ISON so I can’t reshoot that any time soon. Going for another asteroid at 00:16 hrs but that clear zone is now clouded over also. The clouds aren’t moving in. They’re just appearing.

I’m shut down and closed up by 00:20 hrs. 6 observations are forwarded to the MPC within minutes.

hgp 11:00 hrs, 20 Dec 2012
Pete P.
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Re: Astrometry plus 1st views of comet ISON

Unread post by WCGucfa » Thu Dec 20, 2012 2:40 pm

Good going, Pete!! I KNEW you would come through!
I've posted your image in the comet ISON message I've got in the Imager's Studio.
You've done us proud! We're going to have fun with this one. :P 8)

Bill G.
Comets:40, Best Meteor shwr: Leonids '01, Best Aurora:Oct. '03.
Total.Sol.Eclipse,7/10/72 from Nova Scotia.Annular Sol. Eclipse '94,
Trans.of Venus 2004&2012.,ShoeLevy crash into Jupiter '94.
4/25/66 fireball-9 mag.,SN2011fe,N2012aw,DelphN2013.