Re: [ATM] ATM edge support

[James P Crombie <jpcrombie@pei.eastlink.ca>]

My cad program says about 3mm difference at the edge.  I didn't do any 
calculation myself,  just drew the two profiles.



The Alarm Co. wrote:

>I just toured the McDonald Observatory (part of the Texas Star Party
>festivities) and got a good look at the back end of the 107" scope.  It has
>an astatic cell with about 30 points (the guide wasn't sure of the exact
>number) that looked pretty ordinary.  Here's the interesting thing:  the
>edge supports are also astatic.  It looked like there were about 10 points.
>Since it's on a equatorial mount,  the astatic design should automatically
>compensate for the variable orientation of "down".  Sounds like a viable
>alternative for those who don't want to glue their mirrors in or resort to
>multiple slings.
>I also toured the Hobby-Eberle.  Here's a puzzle (one the guide couldn't
>answer).  Its primary is an 11 meter f/1.5 sphere.  How much difference in
>sagitta would there be if it were a paraboloid? (answer withheld as an
>exercise for the reader, and also because I haven't figured it out yet)
>
> *  Best regards, Bob
>*
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>
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