Kde

1 /

H ! : b ;

Fig. 3.53. Maksutov-Cassegrain in "long" and "short" versions with secondary separated from the meniscus. Example with aperture 400 mm, f/3.5 - f/10.71

Fig. 3.53. Maksutov-Cassegrain in "long" and "short" versions with secondary separated from the meniscus. Example with aperture 400 mm, f/3.5 - f/10.71

The spot-diagrams of Fig. 3.54 are, monochromatically, almost entirely limited by fifth order spherical aberration. The aplanatic condition in this design is achieved by adjusting m2: a value |m2| < 3.06 produces "inward" coma, a value |m2| > 3.06 "outward" coma. This has an important consequence for the second variant (secondary mirror coated on the back surface of the meniscus) analysed below. The constancy of the monochromatic spot-diagrams over the field is shown by the d80 values of the energy concentrations (80% encircled energy diameters) for the "short" system. These are given in Table 3.15 for three field heights and three wavelengths.

Table 3.15. dso values (80% encircled energy diameters in ^m) for the "short" system of Fig. 3.53 and Table 3.14

Wavelength

400 nm

550 nm

700 nm

Semi-field height

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