Tuesday, June 28, 2011
I Saw 2011 MD (and I've Got The Pictures To Prove It)
Left image, 2011 MD at 22:46 (local time), when it was moving at 408.78"/min (120 sec exposure with GRAS-12). Right Image, 2011 MD at 23:30 local time, when it was moving at 611.15"/min (120 sec exposure with GRAS-12). The asteroid seems to fade out but its brightness fluctuated probably due to rotation.
Well, some of you might be saying, "so what, all you had to do was put coordinates into a robot telescope, where's the challenge in that?" and there is a degree of truth in that. Mind you, given my inherent fumble-fingeredness, even that can be a challenge. The last time I tried to image a rapidly moving asteroid I neglected to correct for daylight saving time and imaged a patch of empty space. Repeatedly.
But in this case it was more complicated. When I put the MPEC elements into my favourite planetarium programs, SkyMap and Stellarium, the tracks I got back were just rubbish. Peter Lake had actually got some images, and I asked him for help. It turns out that the MPEC generate their ephemeris to a standard epoch, sufficiently far into the future that it messes up with plotting the asteroids track in most planetarium programs (it wasn't me just being dim-witted).
So I went back to the MPEC, and this time I generated an ephemeris using the Global-rent-a-Scope observatory number for GRAS-12 (E03), set the Epoch to 27 June, and generated an ephemeris with positions ever 10 minutes. This was a bunch of numbers, but I could cut and paste the RA/DEC directly into the GRAS system. There was still some uncertainty. The error estimates of the location of the asteroid were quite large, so even the best ephemeris position could be out, and the asteroid was moving so quickly across the sky (even though it was moving slowly with respect to earth) that the time to position the scope could be a factor in catching the speeding blighter (this is why I chose GRAS-12, with a wide field of view).
But it worked! I was rewarded with two streaks as the tiny asteroid streaked across the sky. Although relatively bright (about magnitude 12), it was moving too fast to build up a decent exposure. I would have liked to get another shot, but to my (and the others using GRAS-12 to image 2011 MD) dissapointment , the clouds rolled over cutting us short. Thanks again to Peter Lake and Pete Poulos of Global-Rent-a-Scope for helping me get these shots.
For a nice animation see Dave Herald's video, and Efrain Morales has some nice images. Other images and animations are here. Stunning animation here.