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Proceedings Paper

Alignment Of A Full Aperture System Test Of A Cassegrain Telescope
Author(s): Michael J. Fehniger
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Paper Abstract

The misalignment of the secondary and primary mirrors, in a full aperture Cassegrain test, introduces coma and astigmatism into the wavefront. Equations were derived which relate the magnitude and orientations of these two aberrations to the tilt and decenter of one mirror with respect to the other when tested in an autocollimating mode. By determining the coma and astigmatism, introduced into the wavefront, using Zernike circle polynomial fitting techniques, the tilt and decenter correction can be computed which would optically align the secondary to primary. These alignment equations were verified by using a Space Telescope optical' formula, misaligning the secondary mirror, and calculating the resulting coma and astigmatism in the wavefront. The tilt and decenter, necessary to realign the two mirrors of the Space Telescope were calculated from the derived equations, and found to agree with the perturbed secondary mirror misalignment. An autocollimation test procedure will be described for obtaining the full aperture wavefront of a Cassegrain-type system, both on-axis and in the field.

Paper Details

Date Published: 31 December 1980
PDF: 8 pages
Proc. SPIE 0251, Optical Alignment I, (31 December 1980); doi: 10.1117/12.959446
Show Author Affiliations
Michael J. Fehniger, Eastman Kodak Company (United States)


Published in SPIE Proceedings Vol. 0251:
Optical Alignment I
Richard N. Shagam; William C. Sweatt, Editor(s)

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