Asteroid 2005 yu55
Combination of 31, 1 second images, unfiltered.
SBIG STL-1001E CCD. 20" f/6.8 Dall-Kirkham cassegrain telescope at prime focus.
On November 9, 2011, the near-Earth asteroid 2005 yu55 made a very close flyby of the Earth:- so close that it was actually closer than many satellites! It was predicted to peak at about magnitude 11, making it a very easy object in a telescope. With an expected motion of more than 1 arcsecond/second, the motion would be easy to detect. Since I had a class scheduled to be at the telescope that night, I could not spend much time imaging the asteroid, however the students were fascinated watching it in the telescope as it rapidly drifted past stars. Below is an animation of two series of 1 second images of the asteroid.
The asteroid took about 30 seconds to cross the CCD field which is about 24 arcseconds.