Re: [ATM] Need Design Suggestions for a 16" f/1.1 Spherical Mirror

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

Hi Richard,

(noticed I responded directly, again!)

>Have you looked at D. Lynden-Bell's series of 5 articles
entitled "Exact Optics: A unification of optical telescope
design" starting at Mon. Not. R. Astron. Soc. 000, 1 10 (2001).<


I've found it at

arxiv.org/pdf/physics/0203082

Very interesting, but it will take mi forever

(perhaps a bit longer) to go through it. I'm 

nowhere close to this level of expertise.

There are other interesting possibilities, besides the
simplest, all-spherical 2-mirror 3-reflection design.
If design posted is modified so that the central mirror area (effective 
primary) is aspherised, coma can be elliminated, with the astigmatic blur 
being ~0.010mm 1 degree off-axis, and flat field is retained. Min. c.o. 
drops closer to 50% linear. The specs are only slightly modified:

R1: -900mm
K1: -0.4
primary-to-secondary: -659mm
R2: -1000mm

Here, the mirror needs to be stopped down slightly
less, nearly 40% linear.

Forfeiting flat field, minimum c.o. drops to 40%, with
flat-field blur size bellow 10u 1 degree off-axis, and
as little as 4u on the optimally curved one (-960mm).
The specs:

R1: -900mm
K1: -0.72
primary-to-secondary: -648mm
R2: -700mm

Wonder how difficult it would be to aspherize
the central area of a fast sphere?

These examples almost certainly are not the best there is
of the design. Other possibilities may be open, but what
would really make it interesting is if it would be possible
to significantly increase effective aperture of the design.

Vlad



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