RE: [ATM] Re: Aplanatic Gregorian

["Scott Milligan" <starzkey@charter.net>]

Yes, what you ask is possible, in that the aplanatic Gregorian uses two
ellipsoidal mirrors.  Testing the primary mirror at it's stigmatic
conjugates, however, is complicated by the fact that the conic constant is
nearly, but not exactly -1, so that the long conjugate focus is very long
indeed.  Perhaps a Ross null test would be a more practical alternative.

Scott Milligan

-----Original Message-----
From: atm-bounces@atmlist.net [mailto:atm-bounces@atmlist.net] On Behalf Of
lou krajci
Sent: Saturday, November 27, 2004 11:39 PM
To: Jarvis Krumbein; atm@atmlist.net
Subject: [ATM] Re: Aplanatic Gregorian

>From: Jarvis Krumbein [mailto:jkoptic@juno.com]

>Lou, the figures for both primary and secondary are no harder to do than
>any other surface using the Focault test.

I did not state my desire clearly enough.  I'm looking to see if there is a
Gregorian variant possible that has both mirrors capable of being null
tested at conjugate foci...i.e. they are both ellipsoids.  This means your
optical testing is only null testing with the simplest and minimum of
equipment (and no additional optics)...you only need a light source and a
knife edge.  You don't need to worry about measuring longitudinal aberration
as with the Foucalt test.

Does such a Gregorian variant exist?

>Remember that you can consider
>the primary as a less than fully corrected paraboloid and the secondary
>can be null tested.  Null testing the primary is also possible but
>probably not too practical.  Look at the numbers that Valdimir has
>supplied and you will see what I mean.

I must have not received that particular digest issue of this forum.  Can
someone send what Vladimir posted so I can review it?

Thanks in advance.

Tom Krajci
Albuquerque, New Mexico
---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.801 / Virus Database: 544 - Release Date: 11/24/2004

_______________________________________________
ATM mailing list http://www.atmlist.net/


_______________________________________________
ATM mailing list http://www.atmlist.net/