CCD photometry
CCD cameras have long been used in the production of “pretty pictures” – the wonderful astrophotographs that we see in magazines, books and websites. However, CCD cameras also have a long history of scientific study, and with the plethora of commercial and free photometry software, they have become the mainstay of amateur research activities.
Projects for CCD photometry
Note that like Visual Observing, this area of research within VSS is based around the technique of observing, rather than purely the nature of the objects being studied. Some of the projects below therefore overlap with the research areas that focus purely on specific types of variable stars.
Dual-Maxima Miras
Project Leader: Stan Walker
The Mira stars are an interesting group of variable stars, well suited to visual observing. (And little observed in colours such as UBV) In most cases there is a quick rise to maximum brightness, followed by a slower decline to a rather faint level. The amplitudes are usually quite large, and the periods of 200-600 days make them easy to observe for the casual observer.
Amongst these stars there are a few unusual objects. These are Miras which, at times, show two distinct maxima minima. The most well-known of these stars in the 1960s were R Centauri and R Normae. Since then, two other southern objects have been observed – BH Crucis, discovered by Ron Welch in Auckland, and NSV 4721, now V415 Velorum, the existence of which was drawn to our attention by Peter Williams. The periods of these stars are all in excess of 400 days and usually 500 days. Colour photometry reveals another interesting feature, namely that the first maximum in R Centauri is bluer, hence hotter, than the second maximum, whereas the reverse is the case with BH Crucis.