Re: [ATM] ATM Foucault images

[Mike Lockwood <melockwo@uiuc.edu>]

David,

vorblesnak@peak.org wrote:
>>From: "Stephen Koehler" <s.c.koehler@gmail.com>
>>Here's my best effort at deciphering the astigmatism in your hall of
>>shame #5
> A marvelous analysis clipped for band width ..

It sure was marvelous!  Thanks again Steve.

> So what does this surface look like?  How would one attack this? The usual
> go back and fine grind again aside, how would one remove this astigmatism?
> I see good recognition of the problem and excellant analysis but, what
> would you do with your hands and the lap to take this out?  That is the
> part I never see discussed or suggested.

I did not make the 32" mirror, but I will be fixing it.

The mirror also has numerous large surface scratches all over its 
surface.  So, that fact, combined with the ~3/16" of wedge, means we 
will be de-wedging the blank and then I will be going back to 
(machine) grinding with 220 or 320 grit.  Time to hit the "reset 
button" and start over.

> I had a 12 inch with moderate astigmatism that had been polished in. I
> went to a full size lap, simple 1/3 CoC strokes and polished it out.  It
> took about five hours.  BUT!  I have to admit I did not know what the
> surface looked like I just knew I had to make it regular.

If it took 5 hours with a 12" mirror, I can only wonder how long it 
would take on the 32".....  and I do not care to find out.

	Mike L.

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