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Proceedings Paper

Preliminary results from the longitudinal dispersion compensation system for the CHARA array
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Paper Abstract

The Center for High Angular Resolution Astronomy (CHARA) has constructed an array of six alt-az telescopes at Mount Wilson Observatory in southern California. Together with the central beam combining facility, the telescopes operate as an optical/near-infrared interferometer with a maximum baseline of 330 meters. Due to practicality and cost constraints, some of the long path delay required for path length compensation occurs out of vacuum. A consequence is a spectrally dispersed beam along the optical axis which decreases fringe contrast. To combat this visibility loss, wedges of glass are placed in the beam to chromatically equalize path lengths. Each set of glass wedges is called a Longitudinal Dispersion Compensator (LDC). The design and fabrication phases for the LDC systems are described. Beginning with the material selection process, a glass with similar dispersive qualities to air within the observing bandwidths was selected. Next was the optomechanical design which included custom engineered optical mounts for the glass wedges, high precision translation stages for automated thickness variation and calibration adjustments. Following this, the hardware driver, software controls, and the user interface were written. Finally, the LDC components were assembled, integrated into the Beam Synthesis Facility, and tested. The quantified results are presented and demonstrate an improvement to the interferometric measurements.

Paper Details

Date Published: 21 February 2003
PDF: 9 pages
Proc. SPIE 4838, Interferometry for Optical Astronomy II, (21 February 2003); doi: 10.1117/12.457161
Show Author Affiliations
David H. Berger, CHARA/Georgia State Univ. (United States)
Theo Armand ten Brummelaar, CHARA Array/Mt. Wilson (United States)
William G. Bagnuolo, CHARA/Georgia State Univ. (United States)
Harold A. McAlister, CHARA/Georgia State Univ. (United States)


Published in SPIE Proceedings Vol. 4838:
Interferometry for Optical Astronomy II
Wesley A. Traub, Editor(s)

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