[pkinchington (Peter (Kanga))]

Originally Posted by AdamJL

Hi Peter

The double spikes could be that the image shifted and your stacking software didn't (couldn't?) align those stars correctly.

I think you've got backfocus issues as well, as many stars on the edges are pointing inwards to the centre, indicating that your sensor is a few mm too close. I'm not too knowledgeable on reflectors, but you should be able to get some 0.5-1mm spacer rings to shift your backfocus (at least you can for refractors, so I assume the same for reflectors?)

Thanks Adam I'll check the backspacing on the coma corrector