Mark’s interest in astronomy was sparked by the first moon landings over half a century ago, and he hopes NASA’s return to the moon in the next few years inspires a new generation of space enthusiasts.
After a career in electron microscopy and decades of visual deep space observing Mark now pursues photometry of southern variable stars from his observatory on the NSW mid-north coast. He is currently director of Variable Stars South.
Orbital period changes in close binary stars can be caused by a number of physical processes, including mass transfer from one component to the other or mass loss from the system as a whole through stellar winds. Observed minus Calculated (O-C) diagrams constructed from minima timings of eclipsing binary light curves provides a direct means of detecting and quantifying period changes. In this talk I will analyse O-C diagrams of several stars monitored as part of the Southern Eclipsing Binaries Project of Variable Stars South. True period change will be demonstrated in several cases as well as apparent period changes due to the presence of a third star or orbital precession in eccentric systems.
Southern variables in general are relatively understudied and amateurs using modest equipment can make significant contributions potentially leading to publication in astronomical journals.