The TAL200K 8inch Klevtzov Cassegrain

Tired of being just another member of the enormous pack of SCT and MCT users? Want something exotic? How about a KCT—Klevtzov Cassegrain telescope? This CAT, the TAL200K, now marketed by Russia's Novosibirsk, sounds exotic, but it is actually fairly similar to the Vixen subaperture corrector scopes. The TAL uses a spherical primary and a two-element meniscus corrector lens (a "Mangin" corrector) coupled to its secondary. It is also pretty similar to the Vixens in other ways, including an f/10.3 focal ratio.

Alas, the TAL got off on the wrong foot when it was introduced to U.S. amateurs a few years ago. To begin, the Russian seller at the time, TAL, insisted on packaging the OTA with a crude and shaky Russian-made GEM. More seriously, the original 200Ks were set up to be collimated by adjusting the secondary mirror. Collima-tion, it turned out, was frequently needed by new telescopes after their long voyage from the motherland, and users naturally attempted to put things right. The optical alignment of one of these telescopes via secondary mirror adjustment is a very difficult affair, however, one best suited for skilled hands and an optical bench. Because of this, many TALs wound up badly out of adjustment and delivered poor images. Recently, the design has been modified to allow collimation via the primary, a much simpler operation, but the damage to the scope's reputation had been done.

Like the Vixen, the main problem with the TAL200K is why someone would purchase it. When properly collimated, the KZT can deliver images very competitive with a modern SCT, not usually better than, however. The TALs are robust in construction, but rather crude looking as well. Finally, the 200K uses a standard rack-and-pinion focuser rather than a moving-mirror system, giving the CAT a very small focus range. Few cameras will come to focus with the TAL, and there may even be problems focusing some eyepieces. Due in part to these negatives, the 200K is no longer being sold in the United States. It does remain popular in Europe, where Meade and Celestron SCTs are quite (insanely) expensive and make the TAL200K an attractively priced alternative.

Novosibirsk must be selling some TAL200Ks somewhere, as they have recently introduced a 10-inch version. The company also has apparently wised up about the mount preferences of Western amateurs. Both the 8-inch and the 10-inch are now available as OTAs only.

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