Re: [ATM] Quartz blanks

[Bernard Maugoust <maugoust@free.fr>]

In message <006f01c629ce$b72847f0$fefefe0a@vladimirzx1znp>, 
 "Vladimir Galogaza" <vladimir.galogaza@zg.htnet.hr> wrote:

> Bernard,
> 
> >can anyone here give a specs comparison between quartz and Zerodur?
> 
> Here is something I have:
>                                                Zerodur             Fused
> Silica
> Density g/ccm                           2.53                    2.202
> Young Modulus MPa             90600                 73000
> Poisson's Ratio                       0.24                     0.17
> CTE Per deg C                       2-4 *10^-8        5.2*10^-7

Thanks for those numbers Vladimir. They look to me to be different enough
materials then. Correct?
 
> Mean coefficient of linear thermal expansion (0-50 deg C temp range)
> (From SCHOTT catalog for Zerodur)
> There are 3 classes:
> Expansion class 0          0+/- 0.02 *10^-6/K
>                  class 1         0+/- 0.05
>                 class 2          0+/- 0.10

The test sheet Schott provided with my two 8" (205mm) blanks says -0.03
*10^-6/K. Class 1 pieces I'd say. 19mm thick at the edge BTW.

I think that Mike's purpose is to find at an affordable price thinner than
usual blanks that will both keep an accurate figure with temp. variations and
equilibrate thermally fast enough. Thus avoiding as much as possible changes
of the overall optical train characteristics (we are with 2 mirrors scopes
right).

Question is: can thermal equilibrium ability be easily derived from the
numbers you gave, for comparing different materials? Is quartz beating
Zerodur at that, or the opposite? I don't see Cervit mentioned, was it not
the american equivalent of Zerodur?

Apologies if I push the thread a bit off track.

Cheers,

-- 
Bernard Maugoust 3°59'E 44°28'N

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