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Hyperbolic prime focus astrograph with an RC primary

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#1 Dan_I

Dan_I

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Posted 30 November 2023 - 06:01 AM

Hi,

Ritchey-Chretien optical sets from GSO seem to be of reasonable quality and not too expensive. For instance, APM sells currently a 16" f/8 optical set for €2,990.

I am wondering whether the hyperbolic primary (which is f/3 I believe) could be used also at primary focus or Newtonian focus with a Ross-type corrector, preferably made with off-the-shelf lens? I don't know if the conic constant imposed by the RC formula works also in such configuration. For the 16" version it seems that k=-1.1 (using that primary to secondary distance is 900mm), while for the 8" version k=-1.2 was found there.

It would be a way to get a larger version of the Tak Epsilon astrographs at a reasonable price...


Thanks,

Dan


Edited by Dan_I, 30 November 2023 - 06:46 AM.


#2 Mike I. Jones

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Posted 30 November 2023 - 09:39 AM

What you're describing is a Rosin configuration.  Check out all the Rosin designs in "Post your optical design" thread.  RC primary conics are a little weaker than optimal for Rosins, but they can still be corrected.  However, the corrector lenses won't  be cheap unless you make them yourself.


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#3 Dan_I

Dan_I

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Posted 03 December 2023 - 05:17 PM

What you're describing is a Rosin configuration.  Check out all the Rosin designs in "Post your optical design" thread.  RC primary conics are a little weaker than optimal for Rosins, but they can still be corrected.  However, the corrector lenses won't  be cheap unless you make them yourself.

Thanks Mike, I'll have a look. It the corrector lenses needs to be custom made it becomes a different story...

 

clear skies,

 

Dan




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