Catadioptric dialyte

The catadioptric dialyte is a mirror lens objective or telescope that consists of at least two separate lenses , one of which is mirrored, and thus contains catoptric and dioptric elements. These systems were already considered by Isaac Newton , but were first published by Hamilton in 1814. In the meantime, a number of variants have been found that have a large field of view with low aberrations .

Executions

Hamilton

The Hamilton dialyte (also called Brachymedial ) consists of a front converging lens made of crown glass , followed by a spaced meniscus lens made of flint glass , the back of which is mirrored. Although many aberrations are well corrected, in this simple form it shows strong lateral chromatism. Recent studies show that this can be reduced considerably with a correction lens close to the focal point.

An auxiliary telescope of this type with a 50 cm opening and an additional corrector is located in the Zvenigorod observatory .

Buffoon

Main article: Schupmann Medial Telescope

The telescope developed by Ludwig Schupmann towards the end of the 19th century and referred to as "Medial" increases the distance between the mirrored meniscus lens so that it lies behind the focal point of the front lens. Another converging lens - or a collecting mirror - is located in the focal point. This construction avoids lateral chromatism. However, the optical elements must be tilted relative to one another so that the image can be reached, which leads to other imaging errors.

A telescope with a 30 cm aperture was tested in the years 1900–1901 in the Urania observatory in Berlin ; a version with a 38.5 cm opening installed in the Landstuhl observatory in 1913. Both telescopes were designed by Schupmann himself and contain a further correction lens directly in front of the mirrored meniscus lens: the first version made of flint glass, the later version made of crown glass, which was also readily available at the time and from which the lens is also made. Schupmann also points to an alternative with only one meniscus lens made of flint glass, but with low chromatic aberrations.

The Rathenower refractor with a 70 cm opening followed later, and in 2002 the Swedish Solar Telescope with a 1 m opening.

Wiedemann-Busack-Riccardi-Honders

Systems in the Hamilton arrangement, but with the same types of glass for the converging lens and meniscus lens, have been further developed in various ways. E. Wiedemann designed the "Astrostar" around 1980, in which a compact design was achieved through a back reflection on the one-sided flat converging lens.

In 1998 and 2000, Hans-Jürgen Busack developed two variants, the first with a front light emission, the latter in a Cassegrain arrangement ; He also sketches a Schiefspiegler who avoids the central obstruction of the two arrangements.

The consequence of these designs is that the converging lens is made weaker and an additional lens must be used close to the focus. They have very low optical errors, but on the other hand require very low tolerances of the optical elements and their adjustment to one another.

Systems according to Klaas Honders and Massimo Riccardi are commercially available as telescopes with 30 cm aperture and a field of view of 3 °.

Terebizh

In 2007 Terebizh presented two variants with 50 and 100 cm aperture, which have a multi-element corrector close to the focus. Terebizh's designs are characterized by the fact that the lenses at the light entry position are passed through one more time after the reflection at the Mangin mirror before the corrector is reached. Both have a flat, almost diffraction-limited image, the former with an image field of 7 ° and an aperture ratio of 1: 2, the second with an image field of 10 ° and an aperture ratio of 1: 1.7. The second variant achieves the excellent properties through two lenses at the light entry position.