Re: [ATM] Astigmatism

["David Harbour" <stainless_steel@suddenlink.net>]

Libor-

Do you use a full sized tool for the grinding, and do you grind with the 
mirror only on top? With answers to these questions, I might have an insight 
about what factors may be plaguing you with astigmatism. Of course, that is 
why our intellectual and ideological progenitors specified the "full 
thickness ratio mirror"- the darned thing was too stiff to warp. Also, what 
kind of tool are you using for roughing out, and then fining? It is my 
opinion that for these operations, having the mirror on top of a full sized 
tool, with no extra weight on the mirror's back, will probably prevent any 
astigmatism from being ground in, especially if tool and mirror are 
regularly rotated fractionally. Tell me about the grinding tool; what kind 
of grinding face, how thick, what materials. If you got astigmatism, I 
believe it is most likely you got it during grinding, not polishing. Let me 
know, Libor-

"R-101"/
(David)

----- Original Message ----- 
From: "libor nemec" <liborec.n@seznam.cz>
To: <atm@atmlist.net>
Sent: Tuesday, May 20, 2008 4:02 AM
Subject: [ATM] Astigmatism


>
> Hi guys,
>
> I would like to ask if you have any experiences with machine grinding of
> thin mirrors. I try to get into that for a while and I have problems
> with astigmatism when creating bigger diameters (16", 1" thin
> borofloat). I read somewhere that it is not possible to use machine for
> thin mirrors. Can anyone confirm that?
>
> Can you explain the mechanism how the mirror start to be affected by
> astigmatism when a machine grinding is used? And, whats more important,
> how it can be prevented?
>
> I have to say that my machine has only one excentr. I use full size lap,
> TOT, 1/3 strokes. I parabolize 1/3 and 1/2 polish lap, TOT, W strokes.
>
> Thanks,
> Libor
> _______________________________________________
> ATM mailing list http://www.atmlist.net/
> 


_______________________________________________
ATM mailing list http://www.atmlist.net/