Sixth Catalog of Orbits of Visual Binary Stars:
Calibration Candidates

(last update: 6 November 2013)

This catalog consists a subset of systems from the current version of the Sixth Catalog of Orbits of Visual Binary Stars. It was prepared in answer to requests for lists of binaries which might be used for scale calibration purposes. Stars initially picked for this list included most of the "grade 1" orbits; these are systems having many observations (usually covering more than one orbital revolution), good phase coverage, and small separation residuals. These tend to be closer, shorter-period systems, in some cases resolvable only by large telescopes or multi-aperture interferometers. In order to provide calibrators for smaller instruments, a similar number of wider, long-period systems were chosen as well. Orbital coverage for these wide systems is incomplete, so most were given grades of only 4 or 5; however, since orbital motion is slow, the quoted elements should predict the stars' motions quite well for many years into the future.

As in the main Sixth Catalog, figures are included in order to allow the user to visually inspect each orbit's quality prior to use. An expanded set of ephemerides have also been generated, giving predicted separations and position angles with finer time resolution than in the main catalog (although these ephemerides will obviously still be of little use for very short-period systems).

A few words of warning are in order! First, all "calibration candidate" orbits are NOT of the same quality, however much we would like them to be! Before using a set of elements please examine the elements, figures, etc. carefully to check whether that orbit appears to be of proper scale and sufficient quality for your purposes. Also, using measurements of double stars to calibrate the measurement of other double stars is certainly circular (or, if you will, Keplerian). We strongly advocate the use of other absolute calibration techniques such as a slit mask (cf, McAlister et al. 1987, AJ, 93, 688; Hartkopf et al. 1997, AJ, 114, 1639; or Douglass et al. 1997, ApJS, 111, 289) or at least star trails (for east-west orientation) if at all possible. When double stars are necessary for scale calibration, the set provided should be adequate; however, the measures you determine will only be as accurate as the calibration systems you use. The use of these systems for identification of higher-order motions or submotions is certainly discouraged. Caveat emptor!

This subset of the Sixth Catalog presently includes 81 orbits of 80 systems. See the parent catalog for a description of the grading method and the catalog itself, as well as statistics, etc.

UPDATE: The calibration list has not been updated in recent years, due to lack of staff. If you use this calibration list and wish it to be maintained, please let us know! (You may email us at wds[at] Otherwise, we will assume it is of little use and will remove it from the website.


Your comments regarding either style or substance are welcome. Please inform the authors of any errors you run across in the catalog, any published elements which may better describe any of these systems, or any systems which should be added or deleted from this list. If you have your own ephemeris software, we would appreciate it if you would check your results against ours for a few sets of elements and let us know of their agreement or disagreement.