Re: [ATM] PLOP_Obstruction parameter_What's wrong?

["Mitch" <funnybone101@earthlink.net>]

-----Original Message-----
From: atm-bounces@atmlist.net [mailto:atm-bounces@atmlist.net] On Behalf Of
rugo@iinet.net.au
Sent: Sunday, March 04, 2007 11:36 PM
To: atm@atmlist.net
Subject: [ATM] PLOP_Obstruction parameter_What's wrong?

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.

     Perhaps when leaving out the secondary with an 18 point cell your
center is very well supported and with a secondary factored in it doesn't
take that "good" center into account, bringing down the "overall" support
quality by the amount you mentioned.

     Just guessing, but it "seems" to make sense ;)

Mitch

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