Quote:
Originally Posted by Lognic04
Well, a cassegrain mirror simply is an f2.2 or whatever mirror - if you could make ne, then it would work just as good as a hyperstar (with the corrector and cameta at the secondary position of course) Or maybe you could use a diagonal?
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Sorry to burst the perennial bubbles, but there is ZERO chance that Fastar lens assembly will work with an f/2.2 mirror (spherical or parabolic).
There's a lot more than spherical correction in any optical element. Entrance pupil position, correction of other aberrations (there's FIVE of them in any optical element - read up Seidel Aberrations), it all has a significant impact to final image quality.
Again, no single mirror will work well with Fastar. (and combination of Schmidt plate and spherical primary works as an ELLIPSOID, so not even spherical aberration will be corrected, that is even on axis images will be blurry)
Optics is not that complicated, but neither is that simple. Buy a good book on optics and learn to use any of many free raytrace programs (Beam4 has been made freeware for example
https://www.stellarsoftware.com/). It will save you many hours of disappointment.
Bratislav