Bart replied to the topic 'M 31 - Andomeda Galaxy' in the forum. 2 months ago

Have you considered using a reducer/ flattener? They're not expensive and reduce the effective focal length to 1280 mm with an aperture ratio of 6.3.
With your 2.4 micron pixel dimensions, you're very over-sampled, especially considering the mount and seeing.

Another piece of advice: isolate your SCT tube. Only the tube. This reduces tube currents dramatically!