To: atm{at}shore.net
From: Andy Saulietis 
Reply-To: Andy Saulietis 


Mel writes,


> > Are there any modern adhesives that match particular coefficient of
> > expansions with commonly used glass (plate, pyrex, whatever), that if used
> > with precision ground surfaces to mate, would result in a bond that would
> > not distort the glass and that could survive aluminizing and the vagaries
>of
> > time?

UV cured epoxies for bonding lens elements has been around for a long time,
you can even get versions having differing degrees of hardness and index of
refraction. Once it sets, it's virtually
*impossible* to separate the bonded glass.

Unfortunately, this bond makes a thermal barrier (as would RTV) so there
would be a lot of stress with temp changes if Pyrex or common glass were
used. This is why Zerodur is used to make large composite optics..it can be
welded and its CTE is virtually zero so no stress due to temp variations
across the welds. Not very practical for us, it costs ~$7/cu in.

It seems to me that a composite mirror might be possible if the CTE were
very low & the optics could be figured & used at a well equalized
temperature.


Andy Saulietis
ISS Enterprises
PO Box 19
Mayhill NM 88339


World's first astronomy land development:

http://www.pvtnetworks.net/~iss/starend1.htm
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