I uploaded a video showing the operation of a classic Unitron Weight Driven Clock Drive. This 50 year old device allows a telescope to follow the very slow movement of stars and planets. The stellar motion is undetectable with the naked eye but in a telescope the movement is highly magnified so a tracking mechanism is very helpful. The device works strictly because of gravity, allowing the user to set up the telescope far from any source of electricity. It works much like a old fashioned Grandfather Clock. Like any old mechanical device, many find it fascinating to watch. Please visit http://www.youtube.com/watch?v=agC1aJMBLlA to see the video.