Re: [ATM] More on my Mak-Cass project

[Michael Peck <mpeck1@ix.netcom.com>]

At 14:56 25-06-04, David Whysong wrote:
>My question concerns the baffle tubes. In the schematic, they are solid
>pieces with triangular cross-sections. I was thinking of making them
>simple, straight tubes and adding knife-edge baffles (to the outside of
>the primary / inside of the secondary baffle) to stop glancing reflections
>from slightly off-axis light sources. But I am worried that this could

David:

In general the optimal baffle for the secondary will be conical in shape, 
assuming you want some non-zero size field to be both fully shielded and 
unvignetted. Depending on your application you could make it cylindrical 
and accept some vignetting, or make the secondary larger than it would 
otherwise need to be.

The primary baffle most likely could be made cylindrical without problems, 
but you really should raytrace the design to verify that. But why would you 
want to add knife-edge baffles to the *outside* of the primary baffle?

There's some published literature on baffle design, but what I've seen 
applies to designs with the stop at the primary. The math may be a little 
different when the stop is at the front of the OTA. If you follow my links 
I've simplified baffle design to high school algebra.

Mike Peck


_________________

Michael Peck
email mpeck1@ix.netcom.com
Wildlife photography page http://home.netcom.com/~mpeck1/index.html
Amateur telescope making http://home.netcom.com/~mpeck1/astro/astro.html 

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