Originally Posted by gregbradley
You got the colours very nicely. I can't help feeling with some of your images that your focus is just a little bit off. But then again you are imaging with the relatively "small" chip 8300 which gives larger image scale. Is your focus spot on? Are you confident you got the focus as sharp as it'll go? A robofocus or FLI PDF is handy for an FSQ.
The other possibility is the 8300 chip has small wells so I wonder if the 5 minute subs show the stars as tighter than the 10 minute subs. I notice with my 8300 chip that brighter stars spill over and bloat fairly easily with this chip. If you have low read noise then perhaps 5 minute exposures may end up with a tighter looking image without any consequence to the overall noise and brightness. I am going to explore that aspect myself on neb type shots to see if it produces tighter stars.
Interesting comments Greg, You are not the first to comment on focus but I can assure you focus is as good as it gets. I have been using Robofocus and focusmax and with like comments have gone back to the Bahtinov mask and Bahtinov grabber only to find the autofocus routine in Maxim and FocusMax are spot on. I have even gone to the extent of taking one image each LRGB then refocusing.
I can only put it down to poor seeing here in Mt Beauty. Although a very dark area it does suffer from thermal aberations from the surrounding mountains and often suffers from high level wind blowing overhead while it is perfectly still down here in the bottom of the valley.
There is a marked diference between 5 and 10 minute images but not really in star sizes.
An example of the seeing here: I think I have only had 2 occasions when the FWHM of captured images has been below 3.5 and I have seen another couple but haven't been imaging. Most of the time it is around the 5 mark.
Thanks for the comments. Too many variables.