Observing Double Stars for Fun and Science
Amateurs can still contribute to the study of binary stars.
Why Measure Double Stars?
The main reason for measuring binary stars is to determine the total mass of a double-star system. Why? This information is of crucial importance to theorists working on stellar evolution. Indeed, our understanding has benefited greatly from thousands of measurements made by double-star observers since the time of Wilhelm Struve in the early 19th century.
Remarkably, only two basic pieces of information are necessary to determine the orbit of a double star: the position angle and separation of the pair. The position angle defines the location of the companion (the fainter star in a pair) relative to the primary star. The apparent separation of the primary and secondary is measured in arcseconds.