When I was considering the purchase of the RH200 all these variables influenced the final image train.
For a perfect optical system the Airy Disc size is only dependant on F number. From Clarkvision here
http://www.clarkvision.com/articles/...ml#Diffraction
Table 6
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red= Green= Blue=
0.6 0.53 0.47
micron micron micron
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f/ratio diffraction spot diameter in microns
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2 2.9 2.6 2.3
2.8 4.1 3.6 3.2
4 5.9 5.2 4.6
5.6 8.2 7.2 6.4
8 11.7 10.3 9.2
11 16.1 14.2 12.6
16 23.4 20.7 18.3
19 27.8 24.6 21.8
22 32.2 28.5 25.2
32 46.8 41.4 36.7
45 65.9 58.2 51.6
64 93.7 82.8 73.4
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It is a bit more complicated than this as the Airy Disc is not uniform in brightness across its diameter. Otherwise planetary imagers would have no hope of seeing detail when the Airy disc is 60 micron in diameter at f/40.
The diffraction pattern of a circular aperture is a Bessel function which has a pronounced peak. It is this peak that is just above the noise that planetary imagers are recording to give them contrast. The same thing is happening with extended objects as it is a one to one mapping of the point spread function of the optic to each sensor pixel.
Selecting a camera with small pixels to improve resolution is a bad choice as the stars will saturate very quickly due to small well depth.
The reason bright stars are bigger than dim ones is that the very weak higher orders of the Bessel Function are saturating the sensor.
It is basically a matter of balance. With about 2" seeing my system with 9 micron pixels at 600mm FL gives me 3.09" per pixel. With dithering this can improved by a factor of the inverse of root two back to about the seeing. So it has to be a very bad night for my system to be limited by seeing. The actual resolution is at least twice your pixel resolution. In practice it is far worse.
There is no such thing as a perfect optic. I would go for a high Q sensor with bigger pixels than the so called matching to optic. There is no point having resolution that cannot be recorded for dim objects above the noise and fail to meet resolution because of saturation of brighter stars due to well depth limitations.
Bert