Re: ATM Offner compensator

["Antonio de Ugarte" <de_ugarte@terra.es>]

Then if I understand well, you use a compensator to test the mirror while
figuring, and then take it away when its finished.
If this is the case, then any small error in the compensator would transfer
to the primary mirror... is this practical?

Anyway in the design that I say, the compensator remains in the telescope
after its finished.
I can send a drawing and/or the optical parameters if you are interested.

Antonio

----- Original Message -----
From: "Michael Peck" <mpeck1@ix.netcom.com>
To: <atm@shore.net>
Sent: Wednesday, September 18, 2002 9:11 PM
Subject: Re: ATM Offner compensator


>
> At 17:24 18-09-02 +0200, Antonio de Ugarte wrote:
> >I've been able to see the index through the internet in amazon. It
> >apears in a chapter about "null test using compensators". Maybe
> >someone that has the book (if there is anyone) can have a look
> >at it and tell me about it.
>
> Are you talking about using an RC cass or testing its primary? An Offner
> compensator is used in null testing mirrors. You could use one for testing
> the primary of an RC cass - the most famous example being the HST primary
> (which might make you want to think twice about using one).
>
> As far as I know Offner's name is not associated with field correctors for
> cassegrains, and the design of a field corrector is quite different from
> that of a compensator for null testing.
>
> If it's really Offner's device that you want to know about I'd recommend
> Volume II of Wilson's RTO over Malacara (yes I have both).
>
> Mike Peck
>
> _________________
>
> Michael Peck
> email mpeck1@ix.netcom.com
> Wildlife photography page http://home.netcom.com/~mpeck1/index.html
> Amateur telescope making http://home.netcom.com/~mpeck1/astro/astro.html
>
>