CHARA observers will prepare a list of targets and associated calibrators.  Since calibrators are often faint, poorly studied stars, whose characteristics are not fully known, it is often good practice to include several candidate calibrators, and to use one as a "check star" to confirm the quality of the calibration.

The best calibrators will have similar brightness to the target at both interferometric wavelengths and in the tilt-detection band (normally visible-red), will be located close on the sky, and at similar airmass.

Support for interferometric observing, including choice of baselines and calibrators, is available from the NASA Exoplanet Science Institute at and from the Jean-Marie Mariotti Center at

The possibility of changing telescopes and/or baselines during the night depends on the selection and sequence, and on scheduled parallel observing on other instruments.  Steve Ridgway ( can provide advice on proposal preparation, and for accepted proposals, early discussion with CHARA staff is essential.

Last updated or reviewed August 26, 2011.