Hi Merlin66, I did want to ask you if you were happy with the direction your thread is taking - I don't want to hijack your thread!
janoskiss, thanks for your post - it has made me re-evaluate some of my earlier thinking and calculations - and chase more up to date information. Perhaps its a little too early to show poor old Nyquist the door!
I have to admit that this issue of what is the maximum useful focal length to use with a webcam is something that I've grappled with for a couple of months. I am aware of Nyquists theorem (which says you should sample a 2x the resolution limit) but I see many planetary images that I believe are taken at a higher sampling rate than this - not hard fact, yet, but I'm working on that.
One thing that has been problematic for me is defining the maximum resolution of an optical system - early on I think I was using 'older' definitions (Dawes limits, Rayleigh limits - not sure, have to go back and look). When using these as your definition of maximum resolution modern planetary images with webcams blow the 2x sampling away by a long way! Another definition of maximum resolution I have found is FWHM (Full Width at Half Maximum). I'm thinking that if you use FWHM as your definition of maximum resolution the high res planetary images we see may actually fit Nyquists theorem nicely. Again, I'd like to back that up with some hard facts.
More to follow!
