Thank you for looking and your comments Dave, Rob, Ken and Peter, I appreciate them.
I was quite familiar with ASI120 and ASI174 cameras for Lunar, Solar and Planetary with their smaller chip sizes, which I found were quite suited to the Mewlon series of Dall-Kirkham designs. I was a little nervous stepping up to the larger chip of the ASI1600 as I do get some off-axis coma when using my Canon DSLR cameras, which have either APS-C or full frame sensors.
The lunar shots are crops from the quite sharp centre region, so the softer outer edges have been cropped out.
For the deep sky Nereid frames, I accepted the default settings of The Sky X Pro (Offset=10, Gain=75) as this was a new camera and I have yet to get my head around the various combinations of Offset and Gain settings.
What I did find surprising was when I plugged my Nereid frames image data into the Starizona Exposure Calculator, the recommended sub-frame exposure for my BG sky measurements was 0.04 mins = 2.4 secs versus my 60 sec subs – gulp!
Cheers
Dennis