Calibrators for optical interferometry

Christian Hummel
European Southern Observatory
Karl-Schwarzschildstr. 2
D-85748 Garching

Phone: +49 89 3200 6151


Interferometers measure amplitude and phase of the complex visibility, which, by definition, are unity and zero, respectively, for an ideal instrument in the absence of the atmosphere observing an unresolved star through a monochromatic filter. In reality, the measured amplitude is always smaller due to atmospheric turbulence and instrumental degradation, thus the amplitude measured on a science target has to be normalized by the amplitude measured on a calibrator.

Calibrators are rarely unresolved, and if bright ones are needed, they tend to be big enough to require good estimates of their angular diameter. These are extracted from their photometry, assuming they are described by a single photosphere of a non-rotating star.

Thus, we have two issues in this business: first, to define suitable selection rules based on astrophysical insight, and second, to share data on calibrators especially if they turn out to be unsuitable for any reason.

Service area


Here we compile a list of resources to aid in the selection of calibrators. Clicking a link will open the resource in a new window.


Papers related to the topic
  • A catalogue of calibrator stars for long baseline stellar interferometry (Borde et al. 2002)
  • A catalog of bright calibrator stars for 200-m baseline near-infrared stellar interferometry (Merand et al. 2006)
  • The Palomar Testbed Interferometer Calibrator Catalog (van Belle et al. 2008)
  • Projects

    Ongoing projects to improve the data bases


    Areas of concern, comments, issues...

    Last updated: 9 July 2015 by Christian A. Hummel