RE: [ATM] Maksutov Corrector Cell Design

["Jerry Reddell" <jerry.p.reddell63@sbcglobal.net>]

Actually the material feels realitively soft much more so than walnut
shells. It feels to me more like a foam than a gritty hard substance.....I
know that is not scientific.

It is a volcanic rock which has been "expanded" many many times by
heating....this expansion gives it the very low weight. The expansion is
supposed caused by trapped water and gases which expand during the heating
process as the rock softens.

I expect the light weight, seemingly softness, and  glue / paint to provide
some measure of scratch protection...

Jerry Reddell
Phone / Fax: 806 791 7799




-----Original Message-----
From: Mark Holm [mailto:mdholm@telerama.com]
Sent: Tuesday, November 02, 2004 6:44 PM
To: jerry.p.reddell63@sbcglobal.net; ATM Mailing List
Subject: Re: [ATM] Maksutov Corrector Cell Design


Jerry Reddell wrote:


>I have come upon a  product called 'Perlite' which is a texturing material
>for paint to give a rough finish... I plan to use this in a mixture of
White
>Glue and water to coat the inside of my newtonian tube and then spray paint
>it with dull black paint...It gives a sand texture while being much much
>lighter than sand.
>
>
>
I think I recall that Perlite is a mineral product.  This makes it
probably harder than something like sawdust or ground walnut shells that
have been used for this purpose.  If, perhaps I should say when, some
gets loose and ends up on an optical surface, it may be more likely to
cause damaging scratches.

Mark Holm
mdholm@telerama.com



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