Astronomy Principles and Practice Fourth Edition.pdf

The Schmidt telescope 341
Figure 20.8. The UK Schmidt telescope at Siding Spring, Australia. (By courtesy of the Science Research
Council.)
A development, since the original design of the Schmidt telescope, is the Maksutov–Bouwers
camera. In this design, the aspheric correcting lens is replaced by a negative long-focus meniscus
lens with spherical surfaces. By the correct choice of the curvatures of the lens surfaces, the amount of
spherical aberration produced by the lens can be made to match that of the collecting mirror but with the
opposite sense. The single lens can also be designed to be achromatic, again by the correct choice of the
radii of curvature of the lens surfaces in combination with the correct choice of lens thickness, thereby
providing a lens–mirror combination which is free from chromatic aberration. Whereas each corrector
plate of Schmidt telescopes needs individual figuring, the simplicity of using spherical surfaces in the
corrector lens allows easier production of Maksutov–Bouwers cameras. A simple Maksutov–Bouwers
camera is depicted in figure 20.9.