The Variable Star Search (VSS)
The Variable Star Search utility lets you build a set of images and then automatically
search for potential variable stars (non-moving objects only). In the screen shot on the
left, the program has found a potential variable star. Sometimes many targets are found
but only a one or two might be true variables. As you click on each object in the upper
list, the lower list displays information about the first image in which the star was
found and a plot of the data is displayed. The magnitudes are computed as differential
values using the average value of the comparison stars you select just before the final
search begins. The comparison star average is computed from those chosen stars for each
image, thus eliminating most of the effects of extinction as the air mass of the field
changes through the night.
If you click on the Image tab, you can see the first image in which the target appears
with a small green circle centered over the target.
The plot above indicates a target with a good chance of being variable (in fact, it was
a nice eclipsing binary with some unusual aspects). You would measure the star in Canopus,
where the measuring of magnitudes is more rigorous and where the data is stored for period
analysis and conversion to standard magnitudes using PhotoRed.