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D.H. Berger, W.G. Bagnuolo (CHARA)
In recent years, the baselines of optical and infrared interferometers have been approaching half of a kilometer in length. With increased spatial layout comes new and challenging problems to solve. One common hurdle occurs when observing objects not perpendicular to the baseline. The result is one beam with added path length that must be added to the non-delayed beam such that identical phase fronts are combined together to produce fringes. For several interferometers without the addition of costly and logistically difficult evacuated delay lines, path length equalization occurs in long buildings through the ambient air medium. This causes a beam which is spectrally dispersed along the optical axis. The undesirable consequence is decreased fringe contrast. A solution is to disperse the uncompensated beam by inserting a block of glass to match the optical path lengths for all wavelengths within the observing waveband. A single glass solution is presented for the CHARA Array. Modeling, design and fabrication methods are also considered.
The CHARA Array, a six-telescope O/IR interferometric array operated by Georgia State University on Mt. Wilson, California, was funded by the National Science Foundation, the W.M. Keck Foundation, the David and Lucile Packard Foundation, and Georgia State University. This research is also funded in part by the Michelson Fellowship Program sponsored by Jet Propulsion Laboratory.
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The author(s) of this abstract have provided an email address for comments about the abstract: berger@chara.gsu.edu