Sunday, February 17, 2013
2012 DA14, images of the flyby
|Asteroid 2012 DA14 imaged with the iTelescope T12 in Vela shortly after 18:35 UT (5:35 am Saturday 16 February at Siding Spring Observatory). At this time the asteroid was moving a whopping 2432.75"/minute, that's around 0.6°, or just over the diameter of the full Moon in a minute. Image cropped down from the full size exposure, this is a single 30 second luminance exposure.||Overlay of all 3 images I captured in T12, you can just see the third one as it disappears off the bottom. Images stacked and registered using ImageJ. Click to embiggen.|
This was the most challenging near-Earth Asteroid I have ever imaged, more challenging than 2011 MD, which came within the geosynchronous satellite orbits as well, or 2012 TC4 (0.2 Earth Moon distances) and way easier than 2012 QG42 (7.4 Earth-Moon distances).
What I did right: I used my standard technique, which is to choose a star not far from where the asteroid would be, and set that as the target, then wait for the asteroid to zoom by. "Would be" was the operative word. The asteroid was moving so fast that by the time the telescope slewed to the position were the asteroid was, it would have moved out of frame.
I measured the time T12 took to slew, autofocus and begin imaging in a series of recent images, and used the average time from start of my run to actual imaging (around 5 minutes) to set the telescope position.That worked nicely, and I caught the asteroid in frame.
What I did wrong: 30 second exposures! What was I thinking? The asteroid was bright, and when moving at a hooting 0.6° across a field that is only about 3° wide, you aren't going to get many images (adding in the downtime between exposures), I should have gone for 10 second exposures.
I also should have set up imaging runs for Saturday night on the New Mexico scope, but I was exhausted and had to get up at 3:30 am to do my visual observing, so I neglected that. Mistake.
Animated gif of 2012 DA14 zipping across teh T12 field of view (open in a new tab or window to embiggen).
I got up at 3 am to find cloud, not entirely surprising given the huge thunderstorm we had earlier. I popped in and out until 4:00, then made a serious effort to locate the asteroid.
My original plan had been to set up the 4" Newtonian telescope on mu Velorum and wait for the asteroid to get into view as with the iTelescopes, then manually track it.
But there was so much cloud about that even finding bright stars was a problem. A breif gap would appear and by the time I would try to manually slew to the location the cloud would be over again.
So I abandoned the telescope tried squatting with the 10x50 binoculars on the base of Crater, where the asteroid would come through at around magnitude 7.2. But cloud foiled me again. I did see a few shooting stars and a number of dim satellites (so many!) though.
The sky was paling as nautical twilight passed and I scanned the "leg' of Leo, without much hope and then I saw a brightish object in binoculars, not visible to the unaided eye, moving down the leg of Leo at just the right time. It seemed to be moving a little fast, but checking back the asteroid was moving at 0.9° a minute, which was consistent with what I saw. I've also checked with all satellite overpasses then, and nothing was anywhere the vicinity at the time.
So I'm fairly confident that I saw 2012 DA14 in binoculars, and I got it in T12. WOOT! best NEO campaign to date. (and again, a big thank you to Andrew for his SkyMap utility which allows perople to plot NEO's coming close to Earth which defeat standard plotting routines).
Of course, then I had to pack the scope away, wake MiddleOne and take him to tennis. No rest for the wicked (but I missed the opportunity to do a radio interview on the flyby and the Russian meteor by not checking my email before I took him to tennis...sigh).