Completely updated, this second edition gives a broad review of astronomical photometry to provide an understanding of astrophysics from a data-based perspective. It explains the underlying principles of the instruments used, and the applications and inferences derived from measurements. Each chapter has been fully revised to account for the latest developments, including the use of CCDs. Highly illustrated, this book provides an overview and historical background of the subject before reviewing the main themes within astronomical photometry. The central chapters focus on the practical design of the instruments and methodology used. The book concludes by discussing specialised topics in stellar astronomy, concentrating on the information derived from the analysis of the light curves of variable stars and close binary systems. It includes numerous bibliographic notes and a glossary of terms. It is ideal for graduate students, academic researchers and advanced amateurs interested in practical and observational astronomy.