M42 is a tough target. It's one of those "standard candles", hence presenting an image that rises above above the noise it not easy.
-take the time to do flat fields...there is evidence if vignetting in your data
-work harder on the guiding....the stars are elongated.
-focus. focus....and did I mention focus?
This is the one thing you can really nail. Aim for pinpoints...if the seeing doesn't co-operate...well at least you tried.
-colour balance....pretty good!
Stick with it