Re: [ATM] .707*Radius

[Jeff Anderson-Lee <jonah@eecs.berkeley.edu>]

Mark Holm wrote:

> Jeff Anderson-Lee wrote:
>
>> Also, if you turn off the refocus optimization, PLOP will tell you to 
>> place three points at near 0.7R, to let's not bash on Hindle too hard.
>
> For a 200 x 25, f/6 mirror with 39 mm diagonal, I get 0.642r and 5.93 
> nM RMS with refocussing off.


That's still an 8:1 mirror.  Back in the bad old days, full thickness 
was 6:1.  A mirror of that thickness ratio can be supported practically 
anywhere for reasonable sizes. ;-)

I'm not saying that 0.71R is the *best* place to put the supports, just 
that it's not totally out in left field as was the near the edge suggestion.

Now days we have better tools and can determine better placements, but 
that doesn't mean that every cell built to Hindle's ideas needs to be 
tossed away and replaced.

Jeff


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