m42 questions newtonian first light

[pkinchington]

I shot this when the seeing conditions were less than ideal. There was high level cloud which obscured the running man nebula and I was unable to rectify this - using my limited processing skills. Also the stars are egg shaped on the periphery I am not sure whether this is a coma corrector issue or the winds that were buffeting my 200mm f5 newtonian. What has caused the double spikes on the bright star to the left of m42? Camera used was modded sony A7r mirrorless. About 3h of 120s subs. (Added image showing running man a bit better).

[alpal]

Hi Peter,
nice that you're having a go.
There are 11 videos here to help you process in Photoshop:


https://www.youtube.com/channel/UCJ5b6pFHBGe66vsuSaXb-0A


cheers
Allan

[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?)

[pkinchington]

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

[gb44]

Hi
Double spikes could be from a double star of course.
GlennB