IAU Commission 54: Optical & Infrared Interferometry

Working group on calibrator stars

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

Phone: +49 89 3200 6151
Fax: +49 89 3200 4868
Email: chummel@eso.org

Mission Statement

The working group on calibrator stars belongs to the IAU Commission 54 on Optical/Infrared Interferometry, under the Division IX (Optical and Infrared Techniques) of the IAU.

Among the tasks of the working group are the coordination of the work on interferometric calibrator data bases carried out within individual interferometer projects, and the overview of resources and tools for observers looking for suitable calibrators.


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.

Current agenda

Running projects Responsible Status Last update/iteration Deadline/comments
External data base format All open 2005-04-26 Format proposal by W. Jaffe
Revival of bad calibrator page CHU closed 2009-04-24 See Merand et al. 2007, ApJ 664, 1093, for another bad calibrator candidate
Presentation in Marseille CHU closed 2010-05-20 2008-06-30

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: 28 April 2009 by Christian A. Hummel