If you took that with a Nikon D700, why isn't it in color? My guess is that if you process that as a color image, you'll see a rainbow effect going through those streaked edges. I've seen that when the flats are not properly matched to the lights.
I don't really know why they're black/white, but I think it is because I captured them with ASIair pro which produces .fit files. I still need help on how to debayer them as I don't understand it.
As for the flats, yes, they do indeed cause the disturbances. Turns out, I have MAJOR vignetting, and when the flats and/or other calibration images are applied they cause these patterns.
I'll soon get my ASI294MC pro and I think that will fix the vignetting.
But I still would appreciate advice on how to debayer images and get color. Do I need to debayer them before I upload them to DSS, or do I do it later, and how do I do it?