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Re: [OM] Comment on resolution, was Third party lenses

Subject: Re: [OM] Comment on resolution, was Third party lenses
From: "Jeff Keller" <jrk_om@xxxxxxxxxxx>
Date: Thu, 21 Aug 2003 08:58:20 -0700
My very limited knowledge of Maksutov lenses was that they had a
pronounced spherical curvature to the corrector lens. Is the focal
length/aperture of common camera lenses such that these can be nearly
flat? IRRC the Maksutov was used for slower lenses, the Schmidt
Cassegrain(sp?) for faster?

I believe most of the Celestron lenses are Schmidt Cassegrain.

IRRC the Questar is a Maksutov and has a great reputation.

-jeff

----- Original Message -----
From: "Chuck Norcutt" <chucknorcutt@xxxxxxxxxxx>


>
> The photographic lenses also tend to be Maksutov designs probably
> because the secondary can be designed such that it's nothing but an
> aluminzed spot on the back of the Maksutov corrector lens.  No
> additional mechanical support or adjustments required.  However, I
think
> the Maksutov corrector lens is thick enough that chromatic abberation
> could be a design concern.  Also, over about 90-100mm diameter the
> Maksutov lens begins to get very expensive to manufacture.  The
Schmidt
> corrector plate is so thin and so nearly plano-parallel that chromatic
> abberation is not a worry and (for the last 30 years or so) is
> relatively inexpensive to build in large diameters.
>
> Having said all this I just decided to check the optical layout of the
> Oly 500mm reflex and see that it is not a Maksutov design.  I was
> surprised at the number of refractive elements.
>
> Chuck Norcutt

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