From: "Scott Ewart" 
To: 
Reply-To: "Scott Ewart" 



----- Original Message -----
From: "Dale Eason" 
To: "Jerry B. Hillman" ; 
Sent: Wednesday, August 13, 2003 12:08 AM Subject: Re: ATM Ronchi pics


|
| Jerry,
| I'm no expert. I am just now polishing my first 16" 1 | inch thick
mirror.  But since the list seems so quiet | I will tell you what I think.
|
| I think the mirror is bending on the test stand. It | will cause
astigmatism because the mirror is bending | under it's own weight.  To keep
it from happening I am | using a test stand that has the mirror supports
spaced | at 90 deg from each other on the edge of the mirrror. | Mine isn't
bending that I can see however it is | thicker than yours.
|

    This is a possibility.  Is your mirror in the test stand EXACTLY as it
has been up until you saw this problem?  No pinching?  I see something on
the top left edge.  By the way, I use a sling in my test stand for my
13" x 1" Coulter mirror.
    Also, is your knife edge or ronchi still parallel with your slit?

Scott Ewart




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