Lurie–Houghton telescope
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The Houghton telescope or Lurie–Houghton telescope is a catadioptric telescope. Houghton's original design uses a two-lens corrector at the front of the telescope and a spherical mirror at the back; it was patented in 1944.[1] Instead of the hard to make intricately shaped compound curve Schmidt corrector plate, or the heavy Maksutov-type meniscus corrector lens, the Houghton double-lens corrector is relatively easy to make.
It consists of two lenses: A positive and a negative, set at the front of the telescope which fixes the telescope's aperture. All lens and mirror surfaces are spherical, which eases construction. These lenses are relatively thin, though not as thin as the Schmidt corrector. Light loss and "ghost" reflections, troublesome in the past, are minimal with modern anti-reflective coatings.
Lurie's modification of Houghton's original design places a diagonal mirror on the corrector, to direct the focused light outside the telescope tube in the same way as a Newtonian telescope; doing so allows a shorter focal length and wider field of view.[2]