Re: [ATM] 32" Focal ratio

[Hugues.Laroche@ses-astra.com]

Hi Scott,

>I am going to be ordering a 32" mirror for a dedicated imager.  The
>optical path is going to be folded with a round flat, and the camera
>will be between the primary and the secondary.  I cannot afford RC
>optics so this, I feel, is my best bet.

Large field of view means small f/ratio, so coma. You will
need a coma corrector if you use a single mirror.
And I guess a 32" Schmidt corrector is a little 
bit on the expensive side =:-}
An interesting alternative to the RC is the 
aplanatic gregorian, especially the folded variant
(small flat near the focus of the primary,
concave tertiary outside of the primary path focusing
beyond the secondary). All reflective optics with good
performance at the system focal plane. As always there
are trade-offs, but ellipsoidal mirrors can be null-tested 
in the shop, by contrast to paraboloids and hyperboloids.

My 0.02 Euros ;-)

Hugues
Luxembourg, Europe
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