Multicoloured mess

[kryptonite]

I'm not experienced with LRGB imaging, so thought i'd give it a go on M81. However, when i combine the 4 individually processed integrations i end up with horrible colour hues across the image - they're all aligned and wotnot. Am i running into the issues of light pollution (inside the M25), which i can only remove with aggressive DBE application?  Individual files attached.

[Annehouw]

Could well be light pollution. I have something similar in all of my images from home (although the bottom right corner is a bit extreme, maybe). DBE, ABE or something similar will probably take care of it. 

[kryptonite]

Yeah, that corner is pretty bad and pain to get rid of. Guess i just need to brush up on my PI game...

[wimvb]

The bottom right doesn't look like light pollution. Does it show in your calibration masters (flats and/or darks)? If do, it's setup related. The other gradients are due to light pollution or the moon being close. Which of course, is also light pollution. These are easy to remove with dbe.