Quote:
Originally Posted by Atmos
From memory the DK design works with two hyperbolic mirrors as opposed to having a parabolic primary on the SCT. The CDK also has a corrector (possibly in front of the secondary??).
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Quote:
Originally Posted by Somnium
Hi Colin,
the CDK has a parabolic primary and a spherical secondary. the corrector lives just in front of the focuser so basically smack in the middle of the primary mirror itself.
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Hi Colin and Aidan,
Neither of these are correct. By definition a
Dall Kirkham uses a
concave elipsoidal primary mirror and a
convex spherical secondary mirror. If a telescope has some mirror configuration other than this it isn't a Dall Kirkham. A Corrected Dall Kirkham introduces a sub aperture refractive corrector, to correct off axis aberrations inherent in the standard Dall Kirkham design. The corrector I believe is likely to be a 3 element modified Wynne Corrector.
For those interested the following Cassegrain Telescope Designs have the following mirror configurations:-
Schmidt Cassegrain = Spherical Primary and Spherical Secondary with a full aperture Schmidt Corrector Plate
Maksutov Cassegrain = Spherical Primary and Spherical Secondary with a full aperture Maksutov Corrector Plate.
Houghton Cassegrain = Spherical primary and Spherical Secondary with a full aperture Houghton corrector which is a multi element corrector. Unlike the Schmidt and Maksutov correctors which are single element.
Classical Cassegrain = Parabolic Primary with a Hyperbolic Secondary. A Classical Cassegrain will often have a Newtonian focus point in addition to the Cassegrain focus point where the hyperbolic secondary is swapped out for a diagonal flat.
Dall Kirkham = Ellipsoidal Primary and Spherical Secondary
Press Carmichael = Spherical primary and Ellipsoidal Secondary
Ritchey Chretien = Hyperbolic Primary and Hyperbolic Secondary
Cheers,
John B