or maybe not. The frame is too small to fully judge. ?How do you know that "guiding is good"?
If it is not guiding (and I still think that is a likely culprit) then it might be internal flexure that deflects the optical axis and is acerbated by the reducer. Or maybe external flexure, such as an external focuser. ?I would remove the reducer to see if I could get good images (imaging at prime will let you know if your guiding really is good).
In any event a fairly definitive test to differentiate optical from guide errors is to take very short exps of bright star fields (e.g. < 1 sec). ?That is not enough time to allow guide errors, though it does not eliminate vibrations.
Stan
