Re: Making off-axis optics

From: Chris L Peterson (clp_at_alumni.caltech.edu)
Date: 10/08/04 

Date: Fri, 08 Oct 2004 17:40:26 GMT

On 08 Oct 2004 17:00:08 +0100 (BST), Thomas Womack
<twomack@chiark.greenend.org.uk> wrote:

>>I'm not sure, but I observe that in the case of the Cassegrain, you
>>use the donut part of the mirror, whereas with the off-axis, it's the
>>donut hole that you end up using. That might have something to do
>>with it.

I don't think Brian was referring to the central part of the mirror when he used
the term donut. I think he was suggesting that the way a disk cut from a larger
piece of glass behaves might be quite different from the way a disk with a hole
cut from the center behaves. For a parent with residual stress, that is
certainly likely.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com