I notice when I'm trying to process my data in pixinsight that a lot of the times when doing a background extraction it leaves a halo effect on the image that I can't seem to get rid of. Can anyone give me some pointers on what is causing this? I'm in a Bortal 5 area and the image attached was while there was a pretty bright half moon in the sky so I'm thinking the overall sky might have been too bright and not helping. I'm using an astro modified Canon 450D, 6.3 reducer spaced correctly but no filter and a Celestron dew shield.
This astrophotography is hard work