Re: [ATM] Re: 25" mirror possibilities

[scott <srychnov@chem.ps.uci.edu>]

Dear Vlad,

If I am following the discussion correctly, you are proposing to place 
the flat before the secondary.  I didn't see how this could work until 
I went back and saw that you were referring to a Gregorian mirror 
arrangement.  This strategy would appear to have some advantages in 
terms of baffling and accessibility of the image.  Can you really 
reduce the flat to such a small size and have it work?  Would such a 
configuration work for a Cassegrain?


Has anyone made a system like this?   have a Cassegrain with a Naysmith 
focus, but I have not seen the flat placed before the secondary.  What 
problems would might this lead to?  It sounds like an interesting 
design.

Scott



On Nov 18, 2004, at 12:39 PM, vladimir sacek wrote:
>
> One thing you might consider is to fold the design, by placing a small
> diagonal flat in the focal zone
> of the primary. It would reflect light out to the side, where would be
> located secondary mirror.
> This diagonal flat would be between 1/2 and 1 inch in size (minor 
> axis),
> depending on
> secondary magnification and location, for ~40mm field. The tube would 
> be
> shorter, and the spider
> much less massive. Effective c.obstruction (by the flat in the cone
> converging from the secondary) would be
> approx. 15-20%. This setup would allow for lower secondary 
> magnification
> (about |2| minimum) for
> accessible image, and lower, more stable mount.
>
> The only - but serious - drawback is that it would definitely make
> collimation more difficult.
>
> Vlad
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>
>
--
Scott Rychnovsky
ATM Web page:
http://tlepage.home.mindspring.com/

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