From: Mark Holm 
To: JBHillman{at}ev1.net, atm{at}shore.net
Reply-To: Mark Holm 


Jerry,

I took these dimensions for your mirror from Waldo Kitty's message.  I hope they
are correct.

diameter                16.5 in         419.1 mm
thickness
        .75 in          19.05 mm
f-ratio
                4.6
focal length            75.9 in         1927.86 mm
secondary diameter      2.5 in          63.5 mm
mirror material         pyrex

Plop calculates an 18-point cell, using variable angles, that gives very
good support for this mirror.  The proportions look pretty easy to deal
with.  No narrow triangles.

The RMS residual deformation is 1/250 wave.  That is very good, plenty small enough.

r1 = Radius of circle on which inner three mirror support points lie as a
fraction of mirror blank radius.
r2 = Radius of circle on which the bar pivot points lie as a fraction of
mirror blank radius
r3 = Radius of circle on which the six outer mirror support points lie as a
fraction of the mirror radius.
L = Length of each bar.
B = Base of each triangle as a fraction of the mirror blank radius. A1 =
Altitude of each triangle.
A2 = Altitude of pivot point on each triangle.

r1 = 0.398r = 83.40 mm
r2 = 0.578r = 121.1 mm
r3 = 0.832r = 174.3 mm
L =  0.668r = 140.0 mm
B = 0.438r = 91.8 mm
A1 = 0.405r = 84.9 mm
A2 = 0.135r = 28.3 mm

The dimensions L, B, A1, and A2 are to the support points.  The physical
parts will have to be larger.

Mark Holm
mdholm{at}telerama.com

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