Cool image, John!
Second, I am battling a strange phenomenon that I haven't quite figured out. If I look at each of my 3-minute subs, the stars are pretty close to pinpoint round and yet if I rapidly scroll through my whole set of subs, the image walks across the sensor. I only pause for about 2 seconds between the subs so I am completely baffled as to why I can have sharp star images and still have image walk. It is exactly what you want for dithering…but I'm not doing it! Whoa. I've measured the walk and computed how out of round the stars should appear and (at least on the one data set I measured) it doesn't jive. The stars should be slightly oblong. I'm still scratching my head over what in the world could be causing the scope, the sensor, the optics, or anything else to shift a little between each two second frame. I'll have to go back and look at the camera for this data set to see how much the set moved but I bet it did.
I'm puzzled with the exact same issue with my NexGuide. Have you figured out what was happening?