Hi George, nice job. Only comments I've got are the elongated stars, which
I imagine is down to tracking, and it looks like you've overdone the
sharpening a bit, judging by the dark haloes around the less bright stars.
raymo
If you get the same elongation regardless of sub length, then Colin will be
right, the camera sensor is not perpendicular to the light path, either as
Colin said, focuser sag, or maybe at the connection between the camera and the optical train. I also noticed that you have blue semi haloes over the
top of the brighter stars, which seems likely to be CA from something in the optical train.
raymo
When I have my DSLR on the back with a wider FOV I notice the stars are much worse in the corners and elongation tends to be more fanned out in different directions. A flattener may help with this but I always had a sneaking suspicion something else is at play.
Is there anyway to diagnose flop, maybe rotating the camera to see if the orientation of the elongation changes?
If you rotate the camera and the stars streaking remains in the same direction then you can guess that it is directional. It should also change when you point at different parts of the sky if it is focuser sag.
