Schmidt Newtonians

The Schmidt Newtonian telescope (SNT) has always been an also-ran in the CAT popularity contest. Although the design has some real strengths, only Meade has offered serious SNTs to the amateur. Even there, the telescope's popularity has waxed and waned, with Meade discontinuing SNT production in the late 1980s. With the advent of the LXD55 and the follow-on LXD75, the SNT is back. That is not a bad thing, either. This somewhat un-CAT-like CAT does have some pluses. At this time, Meade is still the only non-custom producer of SNTs.

What the heck is an SNT? Think "mutant offspring of an SCT and a Newtonian." Like the SCT, the SNT uses a spherical primary mirror at one end of the tube and a corrector plate at the other. Unlike the SCT, it does not use a convex magnifying secondary. Light from the primary mirror is instead diverted out the side of the tube to a focuser by a Newtonian style flat mirror tilted at 45°. The secondary mirror's holder is mounted in the center of the corrector plate, just as in the SCT. Since this mirror does not magnify, the "final" focal ratio of the scope is identical to that of the primary mirror, which is usually f/4 to f/5. The benefit of this system is that it yields wide fields without the distorting coma that ruins Newtonian edge-of-field performance.

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