Odd artifacts in my processed image of M31

If you zoom in you'll see the artifacts, especially on M31 itself after I stretched it (although these were slightly noticeable before processing).

You'll also see a small spot that appears darker than the rest of the image in the bottom right corner, this is just due to some spot on my scopes lens that I may not be able to remove (I'll need to take more flats to remove this hopefully).

What I'm primarily worried about is that banding/the circular streaks seen int he image.