Sixth Catalog of Orbits of Visual Binary Stars:
(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
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]usno.navy.mil) 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.