From: "Stathis Kafalis" 
To: "ATM" 
Cc: ,
        "Gottschalk Gert" 
Reply-To: "Stathis Kafalis" 


Mel wrote:
> Otherwise, I see little reason to drop below 3/4 - 1 inch thickness in this
> range of aperture.  The glass is hardly more expensive, the glass being a
> rather small part of the cost of the scope anyhow.

I agree completely. I am not thinking of thinner material but larger
apertures. After some discussions with the Schott people in Germany they
started to deliver Borofloat with 25 mm (=1"), so I why not go to
18-20" sizes with this stuff, since it is cheap, easily available in
Europe (which saves a lot of transport and customs hassle), cools down
quickly, has a good thermal expansion coefficient anyhow (same like Pyrex)
and is free of internal stress (at least I polarizer tested more than 15
blanks in 8"-14" sizes and all were fine).

Scott wrote:
> .... it seems to me that if you can make it (test
> it, figure it), then you can mount it.

Full agreement to this too. Mounting it seems to me relatively easy
compared to making it. I am planing for the 14" a modified 9 point
support optimized by PLOP.


Stathis Kafalis
http://www.geocities.com/dobsonstathis

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