Hi Dan!
You did an excellent picture of M8.
To get even more out of this image you haw to use "flatfieldimages".
Either real flatfields or artificial flatfield images.
I tried to make an artificial flat with your image and after flatfield division the whole image became more flat.
Have a look at
M8_gw
(The flat field process should be better done on the raws!)
The coma corrector would improve the stars in the corners but thats
not so bad at all.
As the bright stars show an additional tiny spike upwards maybe
something is in the imagetrain? (Screw etc...)
Gerald