This is one very nice image Peter.... A shame about the vignetting/gradient/flats artifact in the corners but everything else in the image is really well done. How did you manage to highlight the reflection nebula and get the beautiful 3D effect. It almost looks like a bubble about to burst.
Even with the corners it is a great image. I would think it is a problem with your flats as I have had similar and found flats captured with an average of 23000 produced the best results for me. They have to be the hardest thing to get correct and all you can do is experiment. I actually sat one night and captured 10 different sets of flats after an imaging run one night and just processed the image 10 times then used the set which came out the best. Took a while but it did give me somewhere to start next time and I found they ended up being my flats setting for all future images with my QHY8 and Pro.
This is the post and comments made at the time:
http://www.iceinspace.com.au/forum/s...ad.php?t=56267