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


I would not go thinner than 20 mm for an 8". You could do it, but then
you are asking for more trouble, and this is not advisable for a first
timer project (in my opinion).

Most importand is, that the glass be free of internal stress and this is
not allways the case with normal local glass at this thickness - if you get
it at all. Such glass would be good for the tool.

p.s.
You don't neccessarily need to make it f/10. A good parabolized f/7 or f/8
will perform equally well, and will be more compact.


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

----- Original Message -----
From: "Goran Hosinsky" 
To: 
Sent: Wednesday, May 07, 2003 9:33 PM Subject: ATM First mirror prjoject, how thin?


>
> Hi,
> I am collecting materials for my first mirror project, a 8" f/10 newton
> for planetary
> observations (http://www.arksky.org/newtnotes.htm). My first plan was to
> buy a
> kit but I find that postal rates from the US to the Canary Islands are
> rather
> prohibitive. Now I am thinking of buying a piece of plate glass locally
> and  cut out
> the blank.
> The thinner the glass, the easier it is to find and it is cheaper. What
> is the minimum
> thickness I should look for?
> Goran
>
>
>

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