Well as luck should have it, I'm trying to image atm using a guide scope with an 8"sct imaging at 1800mm fl. I normally use an OAG with np (occassionally have trouble with guidestars but 8-10 sec exp soon takes care of that
) and now I remember why. Last few nights with the guide scope .... np good images... tonight, can't guide worth a fig because of flexure and movement in focuser. Going back to OAG if I can''t sort it out quickly.