This review, “TAL’s 150k and 200k,” appeared in the March 2004 issue of Astronomy magazine.
Among most city-bound amateur astronomers, the idea of lugging a long refractor or large Newtonian reflector great distances to dark skies is far from appealing. Instead, most opt for the more compact design of either a Schmidt-Cassegrain or Maksutov-Cassegrain. These designs, however, have drawbacks such as field curvature. In addition, dew condensing on the front corrector lens can bring an observing session to an early end.
In 1974, Yuri Klevtsov, an optical engineer from Koltsovo, Russia, addressed these issues with a new design. Klevtsov’s design uses a fast focal ratio and a spherical primary mirror like Schmidt- or Maksutov-based designs, but it does not use a large corrector lens at the front of the tube. Instead, Klevtsov’s design has an open tube that uses a two-element “Mangin secondary.”
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