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Re: [ATM] Borofloat 33

Hi Richard,

Yes, Schott's Borofloat 33 glass seems to be very attractive to make 
corrector lenses for Lurie-Houghton telescope. Schott uses micro-float 
technic to make the glass. Ie. the glass is taken out slowly from 
furnace producing very clear, transparent and homogenity glass. The 
glass is very light, if remember right the density is 2,2. Also it is 
chemically very stable material, as well as the expansion rate is as 
Duran50 or Pyrex. Actually it should the same glass as Duran50 but it's 
made by float glass technic.

But, is the homogenity of the Boroflot glass high enough for making high 
quality lenses? I do not know but I'm afraid it is not. Just hope I 
would be wrong! I tested one piece of Borofloat. Backside of the glass 
was convex and the glass was tested through the flat, untouched surface. 
The ronchi lines were very much irrecular. Should that be because of the 
flat surface of the glass was really not an optically flat or was the 
reason the un-homogenity of the glass mass? I do not know for sure but 
would like to say the glass mass..

I'm right now making a 7,4" LH telescope which primary is Borofloat. I 
think for the ATM material of mirrors Borofloat is excellent. There 
should not be any stresses inside the glass. There seem to be only a few 
tiny little bubbles inside my borofloat blank.

Best Regards,
Aki Lötjönen


Richard F.L.R. Snashall wrote:

>Just glancing at the Schott website Schott Duryea Glass 
><http://www.us.schott.com/optics_devices/english/products/flash/abbediagramm_flash.html> 
>and noticed a
>page set I had not seen before: Borofloat 33.  The ecode is 473654; it
>has about half the expansion rate of N-BK7.  Comes up to 1 inch thick.
>
>Wonder if it has high enough quality to be used as L-H correctors and
>be cost effective.
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>ATM mailing list http://www.atmlist.net/
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>  
>

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