A computer-controlled telescope is a regular telescope that has been mounted to a motorized platform. This platform gradually moves through the observation period to compensate for the apparent motion of the sky. The exact path the telescope follows has to be programmed into the controlling computer.
As the Earth turns, the sky above seems to sweep past. This creates a problem for long-exposure astronomy and stellar photography. If the telescope is held stationary, any images taken show only streaks as the stars move past the lens. By carefully moving the telescope, it is possible to cancel this rotation and hold the viewfinder on target throughout the period of observation.