Fw: ATM 3 or 4 vane Spider

["D & D" <d3stars@teleport.com>]

-----Original Message-----
From: Thomas O'Hara, PhD <ohara@azstarnet.com>
To: Art Russell <artrussell@mindspring.com>
Date: Friday, January 08, 1999 10:16 PM
Subject: Re: ATM 3 or 4 vane Spider


>
>Art,
>
>To paraphrase General Philip Sheridan, the only good spider is a dead
>spider. How about zero vanes?  Texereau shows how to make a front window
>in the chapter on Cassegrains. Six inch window of BK7, drilled at center
>for a secondary holder like a Schmidt Cass -- presto! NO SPIKES!  Works
>even better on long focal ratios, for the planets.
>
>Otherwise, all your fine work will have been in vane!
>
>Tom
>

Tom,
Isn't there a reduction of light or filtering of some wavelengths due to the
light passing through the 'vane pane'?

Dave Kasnick