Re: ATM How to Prevent Astigmatism in Thin Mirror?

[Anthony Stillman <atmer@flash.net>]

Ed,

>From the top:

>I'm making my first large thin mirror: 16" f5.2 1.125" thick by hand.

Its a quater inch thicker than mine.


>Should I
>have finished fine grinding TOT with the mirror supported below to insure I
>haven't ground astigmatism into the mirror?

I didn't.  But, I did turn everything a lot.


>Do I need to provide special
>support and polish with TOT or can I polish MOT by hand?

I did, with a piece of plastic grass like door mat from Home Despot, with a
sub-diameter tool and farily aggressively while figuring.



>Will slight hand
>pressure "warp" my mirror?


Yes.  Its kind of fun actually.  Get someone to help you while its under
ronchi or foucault.  Someone you trust.


>
>Do I need a special support sling to use with the Focault tester...

I haven't.

>..., or can I
>stand it on a rack like full thickness mirrors?

I have.




Anthony