Re: [ATM] ATM edge support

[Jarvis Krumbein <jkoptic@juno.com>]

Sorry, but the Hobby-Eberle is not an 11 meter f1.5 sphere.  It is a
collection of 1 meter spherical hex shaped (approximately 16.5 meter
focal length) mirrors which share a common focus to increase the light
collection.  When I visited the site six or seven years ago, I was
surprised at the lack of knowlege of the guides who didn't seem to know
anything about the instruments they were showing.  We weren't allowed to
see the 82" at all and were kept at arms length from the 105"?.

Jarvis Krumbein  < jkoptic@juno.com>

On Mon, 9 May 2005 20:35:33 -0500 "The Alarm Co." <tac@i1.net> writes:
> 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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