[ATM] PLOP_Obstruction parameter_What's wrong?

["rugo@iinet.net.au" <rugo@iinet.net.au>]

Hello all
Can someone enlighten me about a possible 'anomaly' I have found using PLOP.
I appear to find when I run PLOP with, and without, including a figure for an
obstruction (secondary diameter) I get different results. I get a better
result when calculating a cell that does not include the secondary diameter.

For example, the mirror is pyrex 20 inch, 1.61 thick and f/L 90 inch. I want to
design an 18 point cell.

Factoring in a 4.25 inch secondary there is a 1/47 wave PV across the mirror,
with a 4 inch secondary it is 1/49 wave PV while with no obstruction factored
into PLOP the result is 1/52 wave PV.

Some may think that the difference is too small to be an issue, however, I do
not believe David Lewis would have gone to the trouble to include in PLOP the
obstruction parameter if it added nothing of value.

There must be a problem with the way I am interpreting the contour data. I
would appreciate if someone could check this out and advise me, and others who
might also be struggling to get the best out of PLOP.
Cheers
Rugo


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