Abstract

The great flexibility of the 200-inch mirror required the development of new and elaborate support systems to maintain the figure in all orientations. New methods had, therefore, to be devised for testing the mirror in the telescope while on these supports. The final figuring was done on the mountain on the basis of these tests.

To increase the effectiveness of the instrument, corrector lenses were designed by Ross greatly to enlarge the field of the main mirror. Likewise the method of evaporating a reflecting coat of aluminum was developed by Strong to replace the old silvering procedures. Several new optical designs were introduced in the spectrographs to make optimum use of the light collected. These included the use of (1) a composite of four “blazed” gratings to permit a collimator aperture of 12 inches; (2) Schmidt cameras with half-strength corrector plate placed practically in contact with the grating, the light passing through the plate twice (this eliminates many vignetting problems and permits higher speeds and larger fields); and (3) a combination of a quartz aplanatic sphere with a Schmidt camera for the shortest focal-length camera to obtain a much higher speed (F/D = 0.7) than would otherwise have been possible.

© 1952 Optical Society of America

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References

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  1. Don Hendrix, Pub. Astron. Soc. Pacific 51, 158 (1938).
    [CrossRef]

1938 (1)

Don Hendrix, Pub. Astron. Soc. Pacific 51, 158 (1938).
[CrossRef]

Hendrix, Don

Don Hendrix, Pub. Astron. Soc. Pacific 51, 158 (1938).
[CrossRef]

Pub. Astron. Soc. Pacific (1)

Don Hendrix, Pub. Astron. Soc. Pacific 51, 158 (1938).
[CrossRef]

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Figures (5)

F. 1
F. 1

The 200-inch Hale telescope.

F. 2
F. 2

The 200-inch mirror.

F. 3
F. 3

Knife-edge tests of the 200-inch mirror taken under observing conditions with a star as the source; (A, B) one-twentieth second exposure showing air turbulence; (C) forty-second exposure before final figuring on the mountain; (D) eighty-second exposure after final figuring.

F. 4
F. 4

Part of coudé spectrograph as arranged for 8.4-inch camera. (A) Mirror of 18-inch camera; (B) aplanatic sphere; (C) plateholder of 18-inch camera; (D) ocmposite grating; (E) corrector plate of 18-inch camera.

F. 5
F. 5

Sample spectra taken with coudé spectrograph.

Tables (2)

Tables Icon

Table I Final optical tests of the 200-inch mirror.

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Table II Coudé spectrograph cameras.

Equations (2)

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Dfr / d = 3333 mm = 132 inches .
f 2 = d 3 / 8 ,