From: "Stathis Kafalis" 
To: 
Reply-To: "Stathis Kafalis" 


If the links should not be clickable, they are devided by the e-mail
program. You need to put them together again. Or go here:
http://www.astrotreff.de/topic.asp?TOPIC_ID=3338 (German text but same
pictures)

> Nice pictures.
> How did you exactly made them.
> Specificaly, How big was polariser (width x height) and how far from the
> mirrors back.

This are 48 mm photo polarizer filters. One filter was put into a slide
projector (instead of a slide)
The blank was 2 m away from the projector. The second filter in front of
the camera was another  1 m away from the blank. I think the distances are
not critical. It works with other distances too, as long as the blank is
fully iluminated by the projector beam.


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

----- Original Message -----
From: "Galogaza" 
To: 
Sent: Saturday, May 03, 2003 9:02 AM Subject: Re: ATM Internal stress of blanks


>
> Hallo Stathis,
>
> Nice pictures.
> How did you exactly made them.
> Specificaly, How big was polariser (width x height) and how far from the
> mirrors back.
>
> I do not know much about stress detection by polarized light
> but is it possible that this test detects not only internal stress but also
> nonhomegeneity of the glass. If so than annealing perhaps could remove
> stress from nonhomogen glass leaving it nonhomogeneos. That will explain
why
> you have no problems with this
> on the first sight very stressed glass.
> I remember images of one big historical mirror ( perhaps MtWilson) somebody
> said was made from bottles.  It was visible that mirror was very
> inhomogeneous. My conclusion is that it is possible that inhomogeneity is
> compatible with nonstressed glass.
>
> Comments appreciated.
>
> Vladimir.
>
>
>
>

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