Quote:
Originally Posted by glend
Thanks for that link Allan. I wonder if the calculations can apply to my mak-newt as well, which has a rather small central obstruction of 26% and no spider as itts mounted directly on the corrector plate. The mirror in the mak-newt is a spherical and not parabolic. I will hwve to read that article carefully.
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Yes the formula applies to all obstructions:
Contrast factor = CF = 5.25 - 5.1x - 34.1x²+ 51.1x³
where x is the obstruction ratio.
So the maximum contrast factor you can have is 5.25 for any telescope.
cheers
Allan