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Proceedings Paper

Imaging performance of the Hobby-Eberly Telescope
Author(s): Povilas Palunas; Phillip J. MacQueen; John A. Booth; Robert Calder; James R. Fowler; Matthew D. Shetrone; Stephen C. Odewahn; Pedro Segura; Gordon L. Wesley; George Damm; Jerry Martin; P. Samuel Odoms
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Paper Abstract

The HET is a modified Arecibo-style telescope with a segmented spherical primary and a four-mirror spherical aberration corrector (SAC). Objects are tracked by driving the SAC along the focal sphere of the primary. In the original design of the telescope the alignment of the SAC was to be maintained passively. In practice, this could not be done to specifications, leading to degraded imaging quality. We have developed a metrology system to actively control the alignment of the SAC. An autocollimator maintains the optical axis of the SAC normal to the primary mirror beneath it. An absolute distance measuring interferometer (DMI) monitors the SAC/primary mirror distance, maintaining focus. Both systems work at a wavelength of 1.5 microns, well above the operating wavelength of current or planned science instruments and therefore do not interfere with observations. The performance of the system is measured via Hartmann testing. Several upgrades are implemented in the primary mirror control system, including calibration of individual edge sensors, new control system software, and a new method of setting and controlling the overall radius of curvature of the primary array. New techniques were developed to efficiently piston the segments onto the proper sphere radius.

Paper Details

Date Published: 23 June 2006
PDF: 9 pages
Proc. SPIE 6267, Ground-based and Airborne Telescopes, 62673V (23 June 2006); doi: 10.1117/12.672700
Show Author Affiliations
Povilas Palunas, McDonald Observatory, Univ. of Texas at Austin (United States)
Phillip J. MacQueen, McDonald Observatory, Univ. of Texas at Austin (United States)
John A. Booth, McDonald Observatory, Univ. of Texas at Austin (United States)
Robert Calder, McDonald Observatory, Univ. of Texas at Austin (United States)
James R. Fowler, McDonald Observatory, Univ. of Texas at Austin (United States)
Matthew D. Shetrone, McDonald Observatory, Univ. of Texas at Austin (United States)
Stephen C. Odewahn, McDonald Observatory, Univ. of Texas at Austin (United States)
Pedro Segura, McDonald Observatory, Univ. of Texas at Austin (United States)
Gordon L. Wesley, McDonald Observatory, Univ. of Texas at Austin (United States)
George Damm, McDonald Observatory, Univ. of Texas at Austin (United States)
Jerry Martin, McDonald Observatory, Univ. of Texas at Austin (United States)
P. Samuel Odoms, McDonald Observatory, Univ. of Texas at Austin (United States)


Published in SPIE Proceedings Vol. 6267:
Ground-based and Airborne Telescopes
Larry M. Stepp, Editor(s)

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