Re: [ATM] Lens after diagonal?

[Gary Fuchs <gary@rcn.com>]

Mostly just trying to learn!

I wasn't looking to minimize the cone of light, just to see if there was 
a way to minimize the secondary obstruction.

 >>Diffraction theory shows that there is not much value in shrinking 
the central obstruction diameter to less that 15%.

Wouldn't that secondary be around half the usual size?

Gary Fuchs

Richard Schwartz wrote:

>I don't  understand why you want to minimize the cone of light?    This is
>only of value in long focus telescopes that are optimized for double star
>splitting or planetary observations.   For those telescopes, you ususally
>don't care about the fully illuminated field of view; all you need is a
>sweet spot at the center.
>
>Diffraction theory shows that there is not much value in shrinking the
>central obstruction diameter to less that 15%.
>
>A long time ago I, too, was interested in having an unobstructed aperture.
>Art Leonard was my hero.   But you can trade the complexities of the Yolo
>and Solano for a couple more inches of primary aperture in a newtonian, and
>you do a lot less work.
>
>. . . Richard
>
>----- Original Message ----- 
>From: "GARY FUCHS" <gary@rcn.com>
>To: <atm@atmlist.net>
>Sent: Wednesday, August 25, 2004 11:32 AM
>Subject: [ATM] Lens after diagonal?
>
>
>  
>
>>Hello,
>>
>>I've been considering (from a perspective of almost no
>>knowledge) the problem of minimizing the secondary
>>obstruction in a standard Newtonian design. Could the
>>following work:
>>
>>Place a lens immediately alongside a much smaller than usual
>>diagonal so that the cone of light, hitting the diagonal at
>>appproximately focus, would be refocused to a point
>>comfortably outside the tube.
>>
>>If this wouldn't work - and I mean "work" in a practical, do-
>>able, giving comparable results to the standard methods, way,
>>why not?
>>
>>Thank you,
>>
>>Gary Fuchs
>>_______________________________________________
>>ATM mailing list http://www.atmlist.net/
>>
>>    
>>
>
>
>
>  
>

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