Overview

All stars are variable – it's just that some of them have not varied appreciably during human history. Every star changes brightness as it ages, and many stars pulsate – that is, they get brighter and dimmer in a regular cycle.

Besides being interesting to watch, variable stars provide opportunities for amateurs to contribute to scientific knowledge. Much of the year-by-year monitoring of variable stars is done by amateurs, and amateurs discover many novae and supernovae. A large telescope is not required; some of the most productive observers use small, wide-field instruments or even binoculars.

Amateur variable-star work is coordinated by the B.A.A. (p. 30) and the American Association of Variable Star Observers (AAVSO, 25 Birch St., Cambridge, MA 02138, U.S.A., http://www.aavso.org). The AAVSO maintains a web site with current information on thousands of stars and issues bulletins about unexpected phenomena.

Besides AAVSO and B.A.A. training materials, two very good guides to variable-star observing are the book Observing Variable Stars, by David H. Levy (Cambridge University Press, 1998), and the chapter on variable stars by M. Dumont and J. Gunther in Patrick Martinez' The Observer's Guide to Astronomy, vol. 2, pp. 775–846. Levy's book is designed for beginners and casual skygazers; Dumont and Gunther's treatment of the subject is more technical.