Re: ATM Offner compensator

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

Both lens are spheric, all surfaces curved in the same direction, so
I guess that it may be more like a Maksuov than a Schmidt corrector,
but you are probably right that it corrects the residual aberrations.
I know that there is a book with a reference to it:
    Optical Shop Testing
    Edited by Daniel Malacara
    Wiley, 1978
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.
    Thank you,

            Antonio

----- Original Message -----
From: "Michael Peck" <mpeck1@ix.netcom.com>
To: <atm@shore.net>
Sent: Wednesday, September 18, 2002 4:35 PM
Subject: Re: ATM Offner compensator


>
> At 12:50 18-09-02 +0200, Antonio de Ugarte wrote:
>
> >I've seen a design of a Richtey Chretien which uses an
> >Offner compensator at the cassegrain focus which is made
> >from two crown elements.
> >Could someone explain to me whar is the purpose of
> >these aditional optical element?
>
> You can correct the residual field aberrations (field curvature and
> astigmatism) of an RC with as few as 2 lenses of a single glass type, or
> with thin aspheric plates with shapes similar to a Schmidt corrector. It's
> also possible to correct atmospheric dispersion with lens elements placed
> near the focal plane.
>
> I've never seen the name Offner associated with these. Aspheric plates are
> called Gascoigne plates. Lots of people have worked on lens based field
> correctors for cassegrains - the most prolific designer is probably Wynne.
>
> Wilson gives a good discussion of field correctors in Volume I of RTO.
> Peter Smith's website has lots of material too as I recall.
>
> Mike Peck
>
> _________________
>
> Michael Peck
> email mpeck1@ix.netcom.com
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>
>