[ATM] Whiffle Tree mirror edge support help needed

[masuch at cia.com.au (Mark Suchting)]

At 07:56 PM 2/23/2004 -0500, Lawrence Sayre wrote:


>Can anyone point me to good examples of Whiffle Tree based mirror cells?
>Sites containing pictures would be great

Judging from your subject line, I take it you are asking about edge supports

There is an example at:

http://www.nightskyscopes.com/site/std_mirrorcell.shtml

Click the small image of the edge support for a larger one.

These manufacturers are using a layout favored by Pegasus optics for 
testing large thin mirrors.  The fulcrums of the two wiffle-tree bars are 
at 60 degrees apart , and the pads on either end of each bar span 30 degree 
apart. This leaves 30 degree gap between the inner two pads . Adding 
another four bars in this layout ( for an equatorial mounting layout ) 
would give 12 pads at 30 degree spacing, something which George Ritchey 
seemed to favor in his famous essay.

I've tested this layout with 20" X 1.6" with horizontal axis and the mirror 
figure held very good.

For edge support in the telescope I'm more in favor of the piano wire edge 
support at 90 degree because it works and is so simple to make . Have 
tested these on a 16" X 1" thick mirror.  I don't see any good reason to 
use slings anymore.  Theres not much practical information on the Piano 
Wire supports on the WWW yet.   Check the archives,    also :

http://www.astrosurf.com/altaz/lateralsupport.htm

In truth these supports  can either be a `machinists wonder' or a short 
length of 1.5mm piano wire poked into a wooden block with a little teflon 
pad on the end.

Hope this helps.

Mark Suchting