12 September 2012 Tracking faint fringes with the CHARA-Michigan Phasetracker (CHAMP)
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The CHARA-Michigan Phasetracker (CHAMP) successfully tracks fringes in 4-telescope and 6-telescope modes when observing high-visibility targets. We have found that our primary targets (Young Stellar Objects) have unexpectedly low visibility fringes (<20%) for most baselines at CHARA, generally below our tracking thresholds. We have undertaken an upgrade cycle in 2011-2012 to re-optimize CHAMP to allow group-delay tracking on the faintest fringes possible. We describe our multi-pronged strategy using special dicroics, new piezo scanners, and our first attempts to explore CHARA J-band made possible by using special metrology-blocking laser filters. CHAMP can now be used with all the combiners at CHARA.
© (2012) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
John D. Monnier, John D. Monnier, F. Baron, F. Baron, M. Anderson, M. Anderson, S. Kraus, S. Kraus, R. Millan-Gabet, R. Millan-Gabet, E. Pedretti, E. Pedretti, X. Che, X. Che, T. ten Brummelaar, T. ten Brummelaar, N. Calvet, N. Calvet, "Tracking faint fringes with the CHARA-Michigan Phasetracker (CHAMP)", Proc. SPIE 8445, Optical and Infrared Interferometry III, 84451I (12 September 2012); doi: 10.1117/12.926399; https://doi.org/10.1117/12.926399

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