RE: [APML] Sort of OT: New Meade Ritchey-Chretien

["Paul M. Rybski" <rybskip@idcnet.com>]

Dear Colleagues,

      Ritchie-Cretien designs are designed to be free of coma and 
astigmatism at the sacrifice of a flat field.  R-C's become 
astigmatic if the primary is misaligned.  Because of the curved focal 
plane, film (or the thin glass plates I used to use on the Yerkes 41" 
reflector) has to be curved to conform to the shape of the focal 
plane.  Since curving glass plates under a vacuum was always fraught 
with breakage, Boller and Chivens introduced field-flattening lenses 
in their meter-class R-C's in the 1960's.  I used such a system at 
the now dynamited Lindheimer Astronomical Research Center at 
Northwestern University in the late 1960's.  The compromise here was 
that the field flattener could not be perfectly achromatic, requiring 
separate focusing for each filter.

Paul



>Hi Chuck,
>
>	It's my understanding that RC's are supposed to have a flat
>field by design.
>
>Steve Barnes
>
>
>
>-----Original Message-----
>  The only thing I don't see is
>a field flattener.
>
>Happy New Year,
>
>Chuck
>
>-------------
>
>>  Hi folks,
>>   
>>  http://www.meade.com/rcx400
>>   
>>  Don't know if anybody's seen this yet or cares, but I thought it
>>  looked pretty interesting...especially since it's an affordable RC
>>  design.  Thought I'd share since it was apparently designed for the
>>  astrophotographer.
>>   
>>  Cheers,
>  > Jason


________________________________________
Paul M. Rybski, Ph.D.
Associate Professor and Chair, Dept. of Physics, and
Director, Whitewater Observatory
Goodhue 320
University of WI-Whitewater
Whitewater, WI  53190-1790

Office FAX:     (262) 472-5633
Email address:  rybskip@uww.edu

"The mind is not a vessel to be filled,
but a fire to be ignited."  Plutarch
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