3.6.3 The Maksutov telescope
We return now to the Bouwers telescope dealt with in § 3.6.1, which, in its pure concentric form, suffers from first order chromatic aberration apart from fifth order spherical aberration and spherochromatism. The first order chromatic aberration is fatal unless a minimal wavelength bandpass is used. Fortunately, this aberration can be corrected, at the cost of perfect symmetry, by the Maksutov form [3.38]. Meniscus solutions have two great advantages over the Schmidt telescope. Firstly, the constructional length is about one third less - unless the stop is maintained strictly at the centre of curvature, an important point discussed below. Secondly, above all for smaller telescopes, a meniscus with spherical surfaces is far easier and cheaper to produce than a Schmidt corrector plate.
In its pure form, the Maksutov telescope only departs from the symmetrical concept of Bouwers (Fig. 3.26) by changing the radii of the meniscus to give a slightly convex form, as shown schematically in Fig. 3.34. This slight
File : C:\ZEMAX-EE\SCHACRO.RAY Title: SCHMIDT ACHROMATIC CURVEI Date : Wed Apr 26 1995
GENERAL LENS DATA:
System Aperture Ray aining Gaussian Factor Eff. Focal Len. Total Track Lange Space F/# Working F/# Obj. Space N.A. Stop Radius Parax.Ima. Hgt. Parax. Mag. Entr. Pup. Dia. Entr. Pup. Pos. Exit Pupil Dia. Exit Pupil Pos. Maximum Field Primary Wave Lens Units Angular Mag.
Entrance Pupil Diameter ■f
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