RE: [ATM] figuring 10 inch mirror

["Jerry" <wa4guu@verizon.net>]

I'm not surprised. You have removed less than 8 percent of the surface area
from a mirror that has similar slopes up and down over almost its entire
surface. Zone 6 is the only zone close to zero slope. 

Of course it is close to 1/4 wave P-V. But almost the entire mirror has the
same magnitude of slope. Removing 8 percent of much the same slope as the
rest of the surface leaves much the same total slope in the masked mirror.
Had there been more of the mirror that had near zero slope I would think you
would see the Strehl improve more.

Jerry 

-----Original Message-----
From: atm-bounces@atmlist.net [mailto:atm-bounces@atmlist.net] On Behalf Of
Mark Holm
Sent: Saturday, July 23, 2005 10:01 PM
To: atm@atmlist.net
Cc: Wayne Hilliard
Subject: Re: [ATM] figuring 10 inch mirror

Here is an interesting thing.  I tried "masking off" the outer 5
millimeters of radius (10mm diameter) of Wayne's mirror in Sixtets  on
the assumption that getting rid of that much of the turned edge would
make a significant improvement in Strehl.  Surprise!

http://www.atmlist.net/contrib/mdholm-at-telerama-dot-com/W_Hillard_7-22-05_
Sixtests_Para_masked.jpg

Although the turned edge is greatly reduced, the Strehl hardly budged.

Perhaps we need to be more careful with the old advice to mask off
turned edges.  Maybe it isn't the cure-all we have all assumed.

Also, Wayne, if you follow Jim's advice to do multiple Foucault reading
sets, you may find my program FrontSix useful.
http://www.atmsite.org/contrib/Holm/frontsix/frontsix.html
It lets you type in the readings spreadsheet style, then does all the
math and spits it out in either Sixtests or FigureXP format.  You can
even start Sixtests or FigureXP right from FrontSix. (You do have to
tell it the path.)

Sixtests is at http://home.earthlink.net/~burrjaw/public/win6.zip

FigureXP is at http://lerch.no-ip.com/atm/FigureXP_Full.zip

Andreas Reifke's program, Foucault Test Analysis, also processes
multiple test data.  Andreas borrowed Jim Burrows' math from Sixtests.
The results of the two programs are nearly identical, but they have
different feature sets.
http://www.foucault-test-analysis.de/

-- 
Mark Holm
mdholm@telerama.com

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