[ATM] Masking a TDE

[COO <coo_mo@yahoo.com>]

Hi Gang,
 
I've just completed polishing a 6" f7 pyrex blank.  I put it on the foucalt tester and noticed that I have a small 1/8" to 1/16" wide turned edge on it.  I've just put everything away for the day but I kick myself for not measuring the depth of the edge.
 
Anyway, I'm thinking of just "living with it" so I can parabaolize this mirror and the move on to other ATM projects and here is my question:
 
I've heard alot about masking the TDE (see Berry and Kreige regarding large thin mirrors) but I've never seen any info on how this is done.  Do I paint the aluminzed mirror.  Do I build the mask into the mirror cell via some sort of vignetting device.
 
Can any one point me to info regaring some easy/elegant/effective masking techniques.
 
thanks
 
Joe O'Brien
 

		
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