From: "Jerry B. Hillman" 
To: 
Reply-To: "Jerry B. Hillman" 


Hi all,
I have a 20" square piece of 5/8" plate glass sitting here
waiting to be cut into sections to start making the secondary for this
16.5" telescope. Although it cost me nothing since I rescued it from
the dumpster about 7 years ago, it would be expensive to replace.  Two of
the corners have cracked diagonally about 1/2" in from the edge so I
know the glass is not tempered. I also checked it with crossed polorizers
for stress. No problems there. I hope to be able to cut what I need for the
secondary, etc. and still have enough glass left to pass along to ATM's for
small mirrors. It is thick enough for up to about a 6" mirror. Perhaps
eight in the hands of a skilled ATM.
My biggest question. How do I cut this glass.  I have cut window glass
before with no problems, but it is only 1/8" thick.  Is the procedure
the same for thick glass?  I will buy a new glass cutter, but I don't want
to destroy this big piece of glass.
My second question. I know I need three pieces for interference testing.
How much do I need for the whole process?  Comments and help are
appreciated. This is a new venture for me. Clear skies, Jerry

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