Abstract

Most modern reflecting telescopes have relative apertures of about f/3 and f/8 for the primary and first secondary foci in accordance with the suggestions of Bowen. The angular field which can be used at the first secondary focus is limited by the size of available plates for large instruments but can approach ±1° for smaller systems. The factors influencing the choice of the field corrector system in the first secondary focus are discussed. It is an important point whether the Ritchey-Chrétien form of the mirrors is strictly maintained—giving an optimum field without the corrector—or whether the aspheric constants are allowed to vary as free parameters. The differences are small but significant. The performance of a number of secondary focus correctors consisting of one, two, and three elements is discussed, spot diagrams being given in each case. Systems with fixed Ritchey-Chrétien mirror constants are inferior to those with free mirror constants. Test methods for the manufacture of the mirrors of telescopes of this type are compared. A doublet type corrector is suitable for compensation testing of primary mirrors or for secondaries tested from the back, but the testing of the latter from the front is more difficult. Several possible techniques are discussed.

© 1968 Optical Society of America

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References

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  1. I. S. Bowen, Publ. Astron. Soc. Pacific 73, 114 (1961).
    [CrossRef]
  2. C. G. Wynne, “Ritchey-Chrétien Telescopes and Extended Field Systems,” Conference on Astronomical Optics, Imperial College, London, July, 1967.
  3. H. Köhler, Appl. Opt. 7, 241 (1968).
    [CrossRef] [PubMed]
  4. D. H. Schulte, Appl. Opt. 5, 309 (1966).
    [CrossRef] [PubMed]
  5. S. C. B. Gascoigne, Observatory 85, 79 (1965).
  6. E. Glatzel, R. N. Wilson, Appl. Opt. 7, 265 (1968).
    [CrossRef] [PubMed]

1968 (2)

1966 (1)

1965 (1)

S. C. B. Gascoigne, Observatory 85, 79 (1965).

1961 (1)

I. S. Bowen, Publ. Astron. Soc. Pacific 73, 114 (1961).
[CrossRef]

Bowen, I. S.

I. S. Bowen, Publ. Astron. Soc. Pacific 73, 114 (1961).
[CrossRef]

Gascoigne, S. C. B.

S. C. B. Gascoigne, Observatory 85, 79 (1965).

Glatzel, E.

Köhler, H.

Schulte, D. H.

Wilson, R. N.

Wynne, C. G.

C. G. Wynne, “Ritchey-Chrétien Telescopes and Extended Field Systems,” Conference on Astronomical Optics, Imperial College, London, July, 1967.

Appl. Opt. (3)

Observatory (1)

S. C. B. Gascoigne, Observatory 85, 79 (1965).

Publ. Astron. Soc. Pacific (1)

I. S. Bowen, Publ. Astron. Soc. Pacific 73, 114 (1961).
[CrossRef]

Other (1)

C. G. Wynne, “Ritchey-Chrétien Telescopes and Extended Field Systems,” Conference on Astronomical Optics, Imperial College, London, July, 1967.

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Figures (12)

Fig. 1
Fig. 1

Two-mirror system with single-lens correctors.

Fig. 2
Fig. 2

ESO–Cassegrain spot diagrams. (a) ϕ 3500 mm, f/8.3, field ±0°. (b) ϕ 3500 mm, f/8.3, field ±0.17°. (c) ϕ 3500 mm, f/8.3, field ±0.25°.

Fig. 3
Fig. 3

Two-mirror system with single meniscus corrector lens (tooled radii). (a) ϕ 1524 mm, f/8.57, field ±0°. (b) ϕ 1524 mm, f/8.57, field ±0.35°. (c) ϕ 1524 mm, f/8.57, field ± 0.5°.

Fig. 4
Fig. 4

Two-mirror system with two correction lenses, optimal lens form, free mirror aspherical constants.

Fig. 5
Fig. 5

Two-mirror system with corrector of two quartz lenses. Mirror system constants free. (a) ϕ 1500 mm, f/8.0, field ±0°. (b) ϕ 1500 mm, f/8.0, field ±0.35°. (c) ϕ 1500 mm. f/8.0, field. ±0.5°.

Fig. 6
Fig. 6

Two-mirror system with corrector of two quartz lenses. Ritchey-Chrétien mirror constants. (a) ϕ 1524 mm, f/8.57, field ±0°. (b) ϕ 1524 mm, f/8.57, field ±0.35°. (c) ϕ 1524 mm, f/8.7, field ± 0.5°.

Fig. 7
Fig. 7

Two-mirror system with corrector of two lenses of different glass. Ritchey-Chrétien mirror constants. (a) ϕ 1524 mm, f/8.27, field ± 0°. (b) ϕ 1524 mm, f/8.27, field ±0.35°. (c) ϕ 1524 mm, f/8.27, field ± 0.5°.

Fig. 8
Fig. 8

Two-mirror system with fixed Ritchey-Chrétien constants and corrector of three quartz lenses.

Fig. 9
Fig. 9

Two-mirror system with corrector of three quartz lenses. Ritchey-Chrétien mirror constants. (a) ϕ 1524 mm, f/8.27, field ±0°. (b) ϕ 1524 mm, f/8.27, field ±0.35°. (c) ϕ 1524 mm, f/8.27, field ±0.5°.

Fig. 10
Fig. 10

Two-lens compensation system for main mirror.

Fig. 11
Fig. 11

Compensation system for secondary mirror using spherical surfaces.

Fig. 12
Fig. 12

Compensation system for a set of secondary mirrors using an auxiliary aspheric surface.

Tables (5)

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Table I ESO Type Single Lens Corrector Considered for the 1.524-m System for Vienna

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Table II Meniscus Type Single Lens Corrector Considered for the 1.524-m System for Vienna

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Table III Doublet Corrector for Free Mirror Constants Similar to That Adopted for the 1.524-m System tor Vienna (Both Lenses of Quartz)

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Table IV Doublet Corrector of FK1 and LLF6 with Fixed Ritchey-Chrétien Mirror Constants

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Table V Triplet Corrector with Fixed Ritchey-Chrétien Mirror Constants (All Lenses of FK 5)

Equations (1)

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r H / r P = 1 2 Φ [ ( Φ - 2 ) / ( Φ - 1 ) ] ,

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