I made two light boxes, one for the NexStar11 and a smaller one to use on the ED80. I used this website as a guideline.
Generated this master flat frame:
However, I only achieved about 30% saturation due to the misleading histogram display on the 300D.
I did a min/max stretch on the master flat so that I could see what my dust situation looks like.
Looks like I need to learn how to clean my sensor!
As a control I did the classic twilight sky method and collected 9 flat frames at 1/4 sec ISO 100 (average pixel value around 31000).
Same processing as above. This is the stretched result. Based on this, I'd say that my light box works I just need to increase the saturation next time.