Observing variable stars - stars that change brightness, either in a regular way or unpredictably - is one of the major contributions amateur astronomers make to science. There are 36,000 variable stars listed in the General Catalogue of Variable Stars, so it is clearly impossible for the limited number of professional observatories to target even the majority of them. That's where the amateur astronomers come in - thousands of them turning their telescopes to the sky every night. Variable star observing is the popular 'real science' activity for by amateur observers, and this book provides all the detail needed for newcomers and experienced astronomers alike.