Hi There,
I downloaded your file and had a go at it. There is not really any white balance problem but you have really horrendous gradients. I tried my best with both Pixinsight and
APP but just could not resolve them - below is the best I could get.
I am not really sure whats causing them - the initial raw stack has a fairly even gradient which I think is probably your
LP. When thats removed the underlying funky radial gradients show up and its beyond my ability to resolve. Sorry! If i was to guess, I'd say it could be internal reflections - do you have a bright point light source close to your rig - like a street lamp or security light? You also have quite bad
CA and bad shaped stars out at corners - maybe try stopping your lens down a bit?
I hope that maybe helps a bit.
This is the best I could get to. I did try further background extraction but really it was making it worse.
Scope: Skywatcher Evostar 80ED (SW 0.85 FR/FF) on a SW NEQ6Pro
Guiding; SW Evoguide 50ED, ASI 120mm mini
Meade 8" LX200 GPS on wedge (Guided with a cheapo 50mm guidescope and a ZWO ASI 120mm mini)
Sharpstar 61EDPH II (with dedicated 0.8 reducer) with wiliam Optics 32mm uniguide
Camera: ASI2600MC pro. QHY 163M with ZWO 7nm NB filters, Canon EOS700D astro mod
Secondary mount: Skywatcher StarAdventurer
My Astrobin
https://www.astrobin.com/users/mackiedlm/