A Prototype Visible Imager for the CHARA Array

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Session 26 -- Detectors and Telescopes
Display presentation, Tuesday, 31, 1994, 9:20-6:30

[26.09] A Prototype Visible Imager for the CHARA Array

N.H. Turner, T.A. ten~Brummelaar, \& H.A. McAlister (CHARA/GSU)

\noindent Unique among multi-telescope interferometers (i.e. three or more telescopes) under design or construction, the CHARA Array divides the tasks of visible light imaging and fringe tracking between independent sub-systems. This approach enables us to experiment with inexpensive ways of getting all phase closures simultaneously using single-mode optical fibers. In the CHARA Array, seven equally spaced, 25 mm diameter, tip-tilt corrected and path length equalized beams will each be injected into their own single-mode optical fibers. The other ends of the fibers will be mounted into a non-redundant and one-dimensional (1D) pattern which forms the input of the beam combiner spectrograph. The spectrograph forms fringes along the axis parallel with the 1D pattern and disperses the fringes spectrally along the perpendicular axis. Standard processing packages (such as AIPS) have algorithms to handle non-redundant aperature mask imaging.

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\noindent We present results of experiments using a three-element prototype of the above mentioned imager to investigate the feasability of the seven-element version. Specifically we wish to find out: (1) the coupling efficiency of a collimated beam to the single-mode optical fiber, and (2) the stability of the apparatus, both with respect to vibration and long term calibration.

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