RE: [ATM] .707*Radius (long)

["Donald Good" <donald.good@comcast.net>]

There is little noticeable effect between .4 and .6 as long as the glass is
thick enough.  The thinnest I used in the examples was 10:1 (e.g. 1" thick
for a 10" mirror, or 2" for a 20", etc.).  For precision work like
astrophotography, 10:1 may be too thin and .6 may be too far from optimum
for a 3 point support.  If you go thinner, you should be close to the PLOP
recommendation and use more support points.  But high precision is not
necessary.  Rounding off PLOP measurements to 1/4" or 1/2cm is no problem at
all as long as all similar pieces are identical.

> -----Original Message-----
> From: Ken Hunter [mailto:atm_ken_hunter@yahoo.com] 
> Sent: Saturday, December 04, 2004 7:56 AM
> To: Donald Good; ATM
> Subject: RE: [ATM] .707*Radius (long)
> 
> Very good description of what you were explaining. I 
> understood it completely (which is scary) up to the numerical 
> part where my public school education starts complaining. I'm 
> sure your numbers are correct so I'm concluding that the 
> support points can be anywhere along the 3 radial lines 
> between r.4 and r.6 ... is that correct?
> 
> Ken Hunter

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