Sunday, November 20, 2011

Chasing The Elusive Orbital Dirt Clod

I tried to chase an asteroid that passed very close to Earth in early November 2011; asteroid 2005 YU55.
That is will how I will remember this years from now; my first attempt to image a near Earth object (NEO). Not that it went well, but like any attempt that results in a degree of failure, it was a learning experience. 
It was the evening of the 8th November, 2011. My quarry was coming out of the western sky, very faint, not distant in astronomical terms. It would be one of the smallest objects I've ever attempt to image.
For the task, I was using my Samsung CCTV camera. This camera is fairly sensitive, and can take a series of 5 second exposures that can be stacked. It actually does that on the fly. To capture the images, I chose to use an old reliable method, a Macintosh set up for video capture. For years, my main choice was a heavy, but solidly proven, Macintosh 5260. At over 20 kg in weight, lugging it around was becoming a burden, so a few years back I located a USB video capture unit that works with new Macs, such as our old iBooks. Caveat; it only works with pre-OS X operating systems, so our Bondi Blue iBook would be the computer used. 
I was setup and running by 7pm that evening, using the hood of my Volvo as a base. According to the charts, the asteroid was clearing the main body of Delphinus, though still within its boundaries. It was at that time that the camera was aimed in, zoomed and focused. With exposure set, I waited.
There were scudding clouds blowing in from the east, but the sky was fairly dark. The Moon was still low. The camera was working fine. At the settings I chose that night, the trees in the backyard could be seen, pale orange from distant sodium lamps and blurred, their wind blown motion streaked together. They were ghost.
All the stars in Delphinus were visible, and the camera was easily catching the fainter ones. Screen capture was set to 640x480, though the camera was feeding in closer to 500 lines of horizontal resolution. 
At around 7:30pm, I saw a tiny streak.
It was small and faint, and the software was having a hard time discerning it from noise. But it was there. I waited to see if the camera and software would work together long enough for me to attempt a capture. The streak was where the asteroid should have been, but I needed to capture it for proof. It was heading east into Pegasus and a rising, brilliant gibbous Moon. It would be lost soon.
I opened the screen dialog box and attempted to freeze the image.
I got an error message.
That occasionally happens on all computers, so I tried again.
Same result.
This was not at all welcomed; when did it begin doing this? More importantly, why now? Especially now?
Then another anomaly emerged. The software appeared to be freezing at points, and when it would resume, it would jump with a blur.
Taking a guess, I reduced image size to 320x240 and tried again.
It froze the image, but there was a processing problem. Instead of what the camera was capturing, I got what can be best described as psychedelic line noise. I tried again... and again. Finally, success, and the image was saved. 
After doing this a few times, I decided to open up an image on the computer and zoom in. 320x240 resolution is extremely low, and for the image type, plenty of artifacts are certain to show up. They did; stars became blurry sets of pixels, and the background became a mosaic of very dark, multicolored squares. The asteroid was lost in all that noise.
By this time, the Moon had risen higher and was lighting up the sky. My neighbor John came over and witnessed the latter parts of the operation, so I turned the camera on Jupiter, which showed two of the Galilean satellites, and then the Moon, after resetting the camera to handle the brilliance. 
An hour later, I offloaded a few of the images in an attempt to study them. Nothing of the asteroid, and at 320x240, little was expected.
The takeaway is that sometimes even tried and true techniques will break down. Aside from my tablet, which carried my star charts, all of the equipment used is better than a decade old. 
Astroimaging isn't my thing, though. I am old fashioned, and the cameras, when they are used, are for the public, to bring in lunar eclipses and the like. Certainly, I could save up and buy a more modern camera. Even after this embarrassment, though, I doubt it.
I am always willing to give it a try, being the astronomical Don Quixote that I am.

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