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


Regarding the 6" dia x 3/8" thick filter plates, I purchased
several for windows, and found them to be not very flat, which is o.k. for
filters in some apps, but you'll need to touch them up, I think.

Colin

-----Original Message-----
From: owner-atm{at}shore.net [mailto:owner-atm{at}shore.net]On Behalf Of
George Anderson
Sent: Sunday, June 01, 2003 11:19 PM To: atm
Subject: ATM Schmidt vs Slevogt



I received the glass for the ~6" schmidt camera that I am planning on
building. For those that are curious or interested Surplus Shed has 6"
f/2 uncoated mirrors which they say are 1/4 wave for $45 (one or two minor
blems). For the corrector I am planning on using a 3/8" thick clear
photographic filter from the same source (cost $9) and as backup I have an
optical glass parallel plate which is 1/4" ($5 same source) thick that
I will trepan. I still have to test the two for stress and striae as well
as measure the sg to try to determine if they are BK7 or similar.
But, while waiting for the glass to arrive I re-read R&V as well as
stumbled across a few websites which touted the advantages of a concentric
cassegrain or Slevogt camera (flat field outside of the tube).
Before I start messing about with Oslo, would a 6" f/2 Slevogt for
35mm be realistic or will the secondary be excessively large thus
substantialy reducing the true speed of the camera? I am just sounding out
to see if the concept is worth persuing and realize that it means coring
the mirror after it is ground and polished.

George Anderson
Montreal Canada

Clear skies and good health

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