Many of the brightest binaries such as Castor, y Leo and 61 Cygni have orbits graded as 4 or 5. These pairs will benefit from continual monitoring and are easy with small telescopes and micrometers. The frequency of observation should be matched to the apparent motion in the orbit, so in the case of Castor, for instance, annual means at the present time still show significant differences and should be continued for some years yet. For y Leo, however, motion is currently very slow and means could be taken every 5 years or even 10 years without detriment. The important point is that the measures should be made since it is by no means clear that the professional community will be doing it. As techniques become more sophisticated, the close and rapid binaries are becoming the focus of attention leaving the wide visual pairs virtually unmeasured.
For pairs wider than about 10'' then most of these systems are probably optical pairs and occasional measures can serve to check on the proper motions of the component stars. It is even possible to find errors in the Hipparcos Catalogue, as Jean-François Courtot has done with his 21-cm reflector and filar micrometer.2
Was this article helpful?