I've been going over the image processing of my recent North America Nebula image and refining part of the processing. One part that I skipped over was the colour calibration. Some software like Pixinsight offer photometric colour calibration. It platesolves and then looks up the colour values of the stars according to online databases such as ones at the AAVSO.

On my first pass I had ignored this due to an error in the image plate solving that is a prerequisite to the process. My ZWO FITs images do not contain adequate data for the process to succeed so you have to seed this part of the process with the approximate location and sensor/optical information. With this corrected I was able to get this photometrically colour corrected version.

I like the close up of the Cygnus Wall feature with calibrated star colours. I haven't validated their accuracy but at least they are not all white.