[Hagar (Doug)]

Duncan , I think this is one of those easy ones. Maxim has an auto stretch feature built into it's screen display. If you open an image it will always try to stretch the image to whatever the preset is. If you open the stretch display window you can select range and you might find your images don't look so bad.
Just one of the reasons I only use maxim for basic capture but better still is Nebulosity.

A few things you must remember when taking flats with a QHY8.
1. The full well depth of the QHY 8 is approx 27,000E ADU therefore your flats should be taken with a maximum pixel intensity/ ADU count of between 9000 and 13500. This is taken accross the entire image not just a point you pick.
2. To achieve reasonable results you must take Bias frames or at least darks at the same duration as your flats to calibrate the flats correctly.
3. Capture your Flats at the same Gain, Offset and Focus and camera position as your light frames.
4. Talking about Gain and offset settings. Lots has been said about both but the easiest way to set them is to use whatever gain setting you like. I personally never went above about 12. Take a bias frame and adjust your offset until the peak of the histogram is just to the right of the left side, sounds a bit Irish but it works. As long as the same gain is used, well in most cases it doesn't matter to much, your offset is now set and should never need to change unless you use some NB filters and then only a small change is required.

Good luck with it all, it's really not that hard, it just seems like it is.