The setup is CCDSoft 5.0, STT-8300M, FW8G-STT, CGE-1100. When autoguiding at a fast rate (0.5 sec), the guide star periodically gets very dim for one frame and the guiding jerks in one directon, then recovers to center within a couple of frames. This all happens inside 2 seconds but is enough to streak the stars. Trouble is, this is intermittent. I've gone several nights with perfect guiding, excellent centering of the guide star, with as little as 0.3 seconds per guide cycle. Then boom! - it starts misbehaving. (And it's not clouds!) Rebooting the whole setup (mount, camera, laptop) sometimes fixes it, but I haven't yet tried to isolate the problem between the three. What am I doing wrong?