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


A 1/4 wave big mirror could yield two better ones if the defect is a smooth
curved departure from flat.

Beware the Twyman effect!

Colin

-----Original Message-----
From: owner-atm{at}shore.net [mailto:owner-atm{at}shore.net]On Behalf Of
Kristopher Barrett
Sent: Tuesday, April 01, 2003 11:33 AM To: atm{at}shore.net
Subject: Re: ATM trepanning secondaries



> Am I nuts? My idea here is to save mucho bucks. I need two 5" minor-axis
> secondaries, and they cost about $600 apiece. Yikes. But I have a line
> on a 11.5" minor-axis secondary for much less than that. Probably the
> figure sucks, but as a proof-of-concept getcha-by solution, it's mightly
> attractive, ... if I can cut two 5" secondaries out of it.

I would suggest using straight cuts to approximate what you want ( make it
a bit larger than you need ), and then bond the diagonal to the face of a
diagonal cut block ( a chunk of wood 5" round and cut diagonally would
be perfect ).

Coat the surface in wax to protect it, and then grind the edges to suit on
a fine wheel.

The big danger here is, of course, cracking. Go slow on the grind.

--
Regards,
Kristopher Barrett    http://www.cotse.net/users/kbarrett

--- BBBS/NT v4.00 MP