Re: ATM 100% illumination and secondary sizing

[spooner@page.az.net (Michael Spooner)]

I'm not sure about real gains of the 2.6" secondary. With a FOV dia. of
0.66", the edge image will be nearly 10 times the size of the Airy disk for
this size Newt. Compound this with problems of eyepieces this far off axis
and illumination drop off may not be that big a deal. It would be
interesting to see these all factored together for different mirrors. Most
studies just figure purely for light drop off.
--Mike Spooner

----- Original Message -----
From: John Lynch <john_p_lynch@hotmail.com>
To: <climber@world-net.co.nz>; <atm@shore.net>
Cc: <John.P.Lynch@gsfc.nasa.gov>
Sent: Saturday, March 17, 2001 6:27 PM
Subject: Re: ATM 100% illumination and secondary sizing


>
> David,
>
> One other thing I forgot to mention:  With a 2.6" minor axis diagonal
> mirror and 12.5" primary, Newt indicates, as you have stated, that
> the obstruction of the diameter of the primary mirror by the diagonal
> is 21%; however, the obstruction of the primary mirror surface area
> by the diagonal is only 4%.  I would consider this very small, and
> the gains you get by using a 2.6" diagonal versus a 2.14" diagonal
> considerably outweigh the minimal increase in obstruction.  By the
> way, using 2.14" in Newt gives 17% and 3% obstruction for diameter
> and surface area, respectively.
>
> John
>
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