Seeing the Light

These days, amateur astronomers are far better equipped — at least electronically — than they were just a decade ago. Many of them have acquired CCD cameras at modest expense and have learned well how to use them to estimate the brightness of variable stars, a process called CCD photometry. This makes for more precise measurements than the “old way,” which was to look at the star, possibly assisted by a telescope or binoculars, but with no other instrument to estimate brightness than the human eye. The target star is compared to nearby stars of known brightness (comparison stars) and a “judgement call” is made. This process is called visual photometry.