Re: [ATM] PLOP 101

[Mark Holm <mdholm@telerama.com>]

Hi Rich,

Both the thickness and diameter of the mirror come into play, and, to a 
lesser extent, the material, f/ratio and secondary size.

For 8 inch diameter, if the thickness is at least 1 inch, 3 pont support 
with the supports at 0.400r will be sufficient.  Down to 15 mm thick, 4 
points is sufficient.  Radius of the support points depends on 
thickness.  At 0.875 inch, it is 0.514r.  At 0.75 inch, it is 0.526r. At 
200 mm diameter and 15 mm thickness, it is 0.531r.

Send me the diameter, thickness, glass type, focal length or f/ratio and 
planned secondary minor axis and I'll run out a couple of designs for you.

The load on the back, compared to the load on the edge does change as 
the mirror is tilted.  The function for each is sine or cosine depending 
on where you define zero.  For back support, the worst case is pointing 
straight up, and that is what Plop designs for.

Mark Holm
mdholm@telerama.com

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