Re: [ATM] Am I there yet?

[Don Bates <dbates59@yahoo.com>]

Bob, Mark, Dale, and other Mirror Gurus:

Please take a minute to give me your opinion on the
condition of my 10-inch f/6.6 thin plate glass mirror
that is nearing completion. Sorry about not being able
to see the images of my  mirror project in my last
message. I just figured out how to upload my images to
the atm file area. The links below should work.

Here is a general look at the surface condition using
the Foucault test:
http://www.atmlist.net/contrib/dbates59-at-yahoo-dot-com/Bates10inch/09_08_2004/Bates1.jpg
The dark line across the top section is caused by the
camera shutter. Bright streak at center is diffraction
effect. 

Here is the FIGURE graph from 2 days ago: 
http://www.atmlist.net/contrib/dbates59-at-yahoo-dot-com/Bates10inch/09_08_2004/Bates10sept082004.jpg

Here is the TEX graph for the same session:
http://www.atmlist.net/contrib/dbates59-at-yahoo-dot-com/Bates10inch/09_08_2004/texgrapj982004.jpg

Based on this information, I did the following:
1) Cold press for 20 minutes
2) TOT, CI stroke, deepen center with edge of tool. 1
time around barrel.
3) TOT, edge of tool over zone 4.43. 1 time around.

Here are the results:
FIGURE:
http://www.atmlist.net/contrib/dbates59-at-yahoo-dot-com/Bates10inch/09_08_2004/09092004.jpg

TEX:
http://www.atmlist.net/contrib/dbates59-at-yahoo-dot-com/Bates10inch/09_08_2004/MIRROR.TXT

It appears that I made the mirror slightly worse by
going from 1/9.54 p-v to 1/5.28 p-v. However, the
slope from the center area to the 60% zone is less
dramatic. 
Here is what I think I need to do:
1) Push down the 85% zone with TOT, edge of tool over
85% zone. 
2) Push down the center some more with TOT, edge over
center area.

Questions:
1) Are my plans for the next figuring session correct?

2) How do you think the edge looks? I have never
really been able to see the diffraction ring all the
way around the mirror at the same brightness. The
Ronchi test looks pretty good, but does show some very
slight bending at the edge. But I think this may just
be diffraction effects. Is it turned at all? 
2) I do not want to make or use small tools, so I am
using the large tool on top, and using the edge to
treat certain zones. How far can I go using this
method?
3) What do you think about the surface condition of
the mirror? Does it look smooth enough with little
micro-ripple?

Thanks for your kind replies. I am trying to make the
best mirror possible for use in a planetary telescope.
Low micro-ripple, perfect edge, smooth figure, and
very little spherical aberration are the goals. Any
advice would be greatly appreciated. Clear Skies!

-Don 





		
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