[ATM] Central hole during polishing

[Balaji Ramani <balaji@netapp.com>]

I have been working on a 10" f/5 Pyrex glass mirror (1.5 inches thick).  I 
have been polishing it with a 1/3 W stroke, both MOT and TOT and frequent 
turnings.  When I put the mirror on the foucault stand, I noticed that there 
is a huge hole in the center.  The hole is about  4.5" in diameter.  To null 
out the hole, I had to move the KE towards the mirror about an inch!

So, I am wondering how I might have gotten into this state and how to fix it?  
I would like to get to a good sphere before I start figuring.  Any 
suggestions, please?

Thanks,
Balaji
  
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