Originally Posted by Astronut
I used computer tracking; Satellite Tracker software by Brent Boshart. It's erratic because there's a lag between issuing a command to the computer to center it up and it being reflected in the tracking of the scope. There's also the issue that whenever the computer "hiccups" and accesses the hard drive the tracking shuts off for a split second before resuming. Getting it to stay on ISS at an equivalent of 200x or so is easy:
Getting it to do that with a 640x480 tiny little chip in a cheap webcam-style video camera at the equivalent of about 400x is difficult due to the tiny field of view and imperfections in the telescope's gears. If you were using an eyepiece with a good field of view like a 9mm Nagler though (even with a 2x barlow), it'd be as easy as the above video.
Brilliant, you explained it so well Astronut! This is why your video image of the ISS wanders around so erratically while your image of Saturn is so perfectly stationary even though of a similar angular diameter and viewed with the same computer tracking! You explained it so well, I couldn't have done better myself! Well done!