Re: [ATM] 16" RCC primary

["vladimir" <svla@isp.com>]

Hi Jeff,

>  How do your 2 
> examples scale up to a ~400mm primary?  What would be their EFL and the 
> size of the secondary and tertiary mirrors?

Here are the radii/separations for 400mm f/4/8.7 system:

R1: -3200mm
to secondary: -960mm
R2: -1500

Back focal distance (from the surface of secondary) is 127mm. 
The min secondary size is 0.4D. Field curvature
is -1460mm with hyperbolic, and -1760mm with parabolic
 primary. The conics K1/K2 are -1.197/-2.5 (coma-free)
and -1/-1.7, respectively. Astigmatism is low in
both; the coma-free variety has the spot size slightly
over the Airy disc diameter at .25 degree (15mm)
off-axis flat, and about 1/3 the Airy diameter on the
optimally curved surface. That beats comparable RC
by about a factor of three, both flat and curved.

One thing to pay attention to is field limitation due to 
the light reflected from the primary. Roughly, the max
field is somewhat smaller than Ds^2, "s" being the
relative smallest secondary size. In this case, the 
available field should be  nearly 50mm in diameter. 

Vlad





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