On November 8, 2011, asteroid 2005 YU55 passed within about 200,000 miles of Earth, coming closer to us than the moon. I decided at the last minute to attempt to photograph the asteroid through my telescope as it passed. YU55's closest approach was expected at about 5:30 PM Eastern US time, a few minutes before sunset. My plan was to try to photograph it as soon after 6:00 PM as possible, when the sky was dark enough. But I didn't really believe I had much chance for success, for several reasons:

I only had about an hour to prepare - when I hurry, I usually make mistakes, and this project would not be tolerant of mistakes. The sky was partly cloudy, not a good sign. The moon was full, and the asteroid was expected to be a very faint object - likely it would be hard to photograph it against the bright sky background, and it would be impossible to see it through my finder scope. I would have to point and shoot, and learn later if I captured the asteroid. My camera's field of view when attached to my telescope is just a little over one degree, and the asteroid's positions at various times near closest approach differed by more than one degree in the charts I could find.

Nevertheless, I set up the equipment and focused the camera with a few minutes to spare. Since I had no means on such short notice of trying to configure my mount to track the asteroid, I decided to track the sky instead, and to let the asteroid drift through the frames, if I got lucky enough to capture it at all. The asteroid's motion relative to Earth would be east by southeast at closest approach, at the rate of about eight arc-minutes per minute. When the mount is tracking the sky, it moves to the west at the rate of about 15 arc-minutes per minute, so the net apparent motion of the asteroid would be over 20 arc-minutes per minute, or about 1/3 of my camera's field of view. I decided to use 15 second exposures, hoping that would be long enough to capture the faint object.

Using data I had downloaded from the International Astronomical Union's Minor Planet Center website, I pointed the telescope to the expected position of the asteroid at about 6:30 PM and started taking pictures. The sky wasn't dark enough yet, and very little was visible in the frames, so I adjusted the telescope's position for the 7:00 PM coordinates and waited. I started capturing images at about 6:55 PM, and at about 6:58 PM I saw a streak appear near the upper left (northwest) corner of a frame, moving east by southeast. I continued acquiring 15 second frames back to back for a few minutes, but was disappointed to see that clouds passed in front of the asteroid's position after the first few frames and continued for a couple of minutes. Then the sky between me and the asteroid cleared, and I was able to see the streak again as it moved out of my field of view.

I tried again using the 7:30 PM coordinates, but failed to capture the asteroid. This image is a looping animation of 16 frames taken around 7:00 PM. You will have to click the link below to view the image in its "original" size in order to see the animation. The asteroid is circled in red as it enters the field of view near the upper left corner. Clouds obscured the view of the asteroid and most of the stars in the fourth frame, and again in the sixth through ninth frames. The reddish color of the clouds passing through the field is due to light pollution reflecting off of the clouds and back to the camera. You can see the asteroid again as a faint streak circled in red as it moves out of the field of view near the lower right corner.