Re: [ATM] Building a 6" f/5, would like some input

["Bob May" <rmay@nethere.com>]

The secondary size depends upon a lot of things.  How much
vignetting will you allow, how big an EP  (in diameter_ do you
want to use, how important do you think that contrast ratio is
and so forth.
The truth is that there is no "standard" value for the secondary
size.  As a result, grab something and see if you're happy with
it.  Newt will give you the fully illuminated and seventy five
percent light circles which can help you make a nice decision for
you and if the smaller secondary works then that is all you
really need.
Check with Newt for vignetting of the FOV by the tube and that
should be eliminated, if possible.  The best point to vignette is
at the secondary but only then at the edge of the field for a low
power EP which will have a large FOV anyway.

Bob May
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