Welcome to IIS Bratislav!
Quote:
|
... every f/4 paraboloid contains f/5, f/7, f/8, f/9 ... ad-infinitum beams already. So if corrector works with well with say f/4, it works with anything slower just as well (in fact better).
|
Seems to make sense. In other words, when you put an aperture stop in front of the mirror, you would expect the same corrector to work at least as well as it does for the entire mirror.
Quote:
|
Coma is a linear function of off-axis distance (coma blur will be twice as big at 20mm off axis compared with 10mm off axis). But magnification is a linear function too - 20mm eyepiece magnifies twice that of 40mm. In the end, what eye sees right at the field stop is the same angular blur.
|
But as you approach the point where the coma blur is comparable with size of the Airy disk, it becomes less obtrusive. Also as the brightness of the image is reduced at high powers (as inverse square of the magnification) I would expect that coma is more difficult to perceive.