From: "CSC" 
To: "Atm" 
Reply-To: "CSC" 


Note that Alan Adler does not recommend large fast thin optics for flexing,
as the tolerances are vanishingly small.  According to Flex, which I'm sure
you've calculated, the tension is about 50 lbs, which is very easy, but the
cell tolerances are in the order of .5% which means some extraordinarily
tight tolerance control.  The wedge is about .001-.002 which is not a
problem.

What jumps out at me is the gravity effect at 120%.  This means that when
the scope is tipped, the figure will change by more than you want.

I think it's possible to make a 14 on the first go, but difficult if you're
by yourself.  I have enough of a challenge at 10" on slow full
thickness mirrors.

I hope you have no other projects and can devote 300% effort and time to this.

Colin

-----Original Message-----
From: owner-atm{at}shore.net [mailto:owner-atm{at}shore.net]On Behalf Of geoff
Sent: Sunday, July 13, 2003 4:16 PM To: ATM List
Subject: ATM 14 inch f/6 or f/5



Hi All

I am machine grinding a 14 inch port hole into a mirror. I will flex this
mirror as it is only 20 mm thick and being my first project am not
confident of figuring it into an acceptable mirror. The major dilemma as I
come near the end of the hogging out is do I aim for a f/6 or a f/5. Would
all you expert please advise me. The non expert advise will be considered
with equal weighting as non experts most likley will give me some good
reason why I should do what the experts say.

Geoff
South Africa

--- BBBS/NT v4.01 Flag-4