Image 1 (left) shows the asteroid YU55 moving through the sky referenced
to the stars. The asteroid's motion leaves a streak because of the high relative speed of the asteroid
compared to the motion of the Earth.
Image 2 (right) shows the telescope tracking the asteroid. Now the stars are leaving streaks because
of the relative motion between the asteroid and the stars.
Both images are 60 second unguided exposures taken with a DFM Engineering, Inc. 16-inch astronomical
telescope located at the University
of Alabama, Tuscaloosa (used with permission of Dr. William Keel, University of Alabama).