Hi Vince,
Since you asked, here's what I see:
- you have a lot of coma which may be a stacking artifact. But because of poor focusing, I can't tell.
- you have star trails on the two bright stars in the top half of the image. I think you have some problem subframes that have been added to the stack which should have been removed.
- The donut holes are offset from the centre of each unfocused star. This means that you'll need to do collimation.
- your stars in the triangulum are saturated because of the long exposure.
- the top half stars are donuts while the centre are points. There is probably a tilt in your image train. Or due to field curvature.
If you're unaware, M42 is actually a challenging target because of the dynamic range required to capture it properly. The faint parts require a longer exposure while the bright parts require a shorter exposure. People usually take two sets of images, one with the shorter exposure so that the stars in the triangulum are not saturated and then combine it with another set with longer exposures.
Finally, if you're a beginner, an SCT is not the recommended telescope for imaging. A wide field refractor will be easier to get started.
Anyway, that's my opinion and as usual YMMV
cytan
P.S. I'd encourage people who have better image capture and processing skills than me to chime in.
P.P.S. SingAstro is a very quiet forum. If you want guidance and criticisms, I'd suggest that you post to cloudynights "Beginning Deep Sky Imaging" forum:
https://www.cloudynights.com/forum/80-b ... y-imaging/
There are real experts there who'll give you a lot better guidance than what I've written above.
