When I use Deepskystacker 3.3.4 to stack my images (the original .CR2 photos) I get a discoloration in the corners and the left and right edges when I edit the final image (autosave.tif). Regardless of the lens used: Canon 85mm f/1.8 squeezed to f/2.5, 70-300L (set to 300, f/5.6) or Televue Genesis prime focus. Using filters does not help: without filter or Hutech IDAS LPS-D1 or not does not make sense. Only using an Halpha filter does not show up the problem, but that is monochrome.
ISO setting does not influence either, whether 400, 1600 or 6400 in all cases it occurs.
Before saving to a file in DSS I align the RGB sliders over each other and, change the histograms a bit (midtones a bit steeper) and set saturation to +15-+20.
Then I use Photoshop CS6 or Darktable for finetuning.
The edge discoloration is always between blue-green and yellow-green (mostly).
When I edit the individual original CR2 subs with Darktable, Photoshop CS6 or Canon DPP 4.0 the problem does not appear.
Using flats in DSS worsens the problem, however when I skip flats I have to edit vignetting manually and I still get the discolored but in a lesser extent.
See on my website
http://skysurfer.eu/skypics1.php
and the photos of Omega Centauri, Rosette Nebula, Running Checken nebula (starting 2nd of 5th row) and the east part of Cygnus (first of second last row in color) and the very last one (Andromeda Galaxy taken yesterday night) have an obvious sign of this UGLY edge dicoloration :-((
It is not the sensor (I had this problem already with the 7d last summer but due to the crop sensor it is less obvious). As said, single frame do not show this issue.
So crop them all to APS-C ? No that is not the solution.
Does somebody know what I am structually doing wriong ?