IMAGING VARIABLE STARS (“PHOTOMETRY”), 21 FEB 2007

R Corona Borealis is my favourite variable star. After all, it’s easy to locate in the bright constellation of the Northern Crown, and it’s almost always about magnitude 6 – ie: at maximum brightness!

You estimate the brightness of variable stars by gauging them against nearby stars of known brightness. The AAVSO has charts for each variable, noting the most suitable comparison stars. Estimating brightness of stars is therefore part art, part science. It’s one of the more important contributions amateurs make to modern astronomy, well worth trying!

If you have a small telescope, an imaging camera and a V filter (a greenish colour) you can collect images of the variable stars and use the results to more accurately measure the changing brightness of variable stars. This is “photometry” and there is free software that will analyse the images to provide accurate readings. Telescopes and cameras are not just for taking “pretty pictures”.

Here’s an image of my favourite variable star, taken this morning with a V filter. R CrB is magnitude 5.9, or can’t you tell?