Figure 5: Commercially available hybrid reflectors
Currently experiencing an upward surge in popularity is the Maksutov-Cassegrainian reflector which is usually imprecisely referred to as merely a Maksutov. It normally possesses the compact size and low weight of the Schmidt-Cassegrainian. I have noticed that some people assume that since the curve on a Schmidt-Cassegrainianís corrector plate is more complex than the Maksutov-Cassegrainianís meniscus, the Schmidt-Cassegrainian is more expensive to produce. That idea is a misconception. Unfortunately, because the meniscus of Maksutov-Cassegrainians has two curved surfaces and the curves are more deeply cut than the single curved side of the Schmidt corrector, they traditionally have cost more than Schmidt-Cassegrainians (whose corrector plates only have one curved surface). The more curved surfaces an optical element has and the more glass has to be removed from it, the more time and expense is consumed producing it. Many observers consider the extra expense worth it since the meniscus changes the light cone cast by the objective mirror in such a manner that the telescopeís secondary mirror can be made smaller than it normally would be. The resulting lowering of diffraction may lead some Maksutov-Cassegrainians to approach the image quality of the apochromatic refractor. The Maksutov-Cassegrainianís new found popularity began with the recent availability of less expensive, high quality telescopes of this type from Russia. Responding to the increasing popularity of the optically superlative Russian-made instruments such as the ones offered by Orion Telescopes and Binoculars, ITE, and Adventure Products, the folks at Meade Optical are now producing some low priced Maksutov-Cassegrainians in their American factories that are also reasonably priced and of fine workmanship. Usually a Maksutov-Cassegrainian has a small reflective circle at the center of the convex back of the meniscus instead of a separate secondary mirror, though this is not always the case.
copyright 2004 Singularity Scientific