This book is an up-to-date and comprehensive account of current observational techniques with particular emphasis on optical astronomy. Dr Walker, a world expert in astronomical instrumentation, has written a complete survey of the basic electromagnetic spectrum. The author discusses the types and sources of stellar electromagnetic radiation and the range of telescopes that are used to observe them. Topics covered include the construction of sensitive low-noise detectors, preservation of image quality, and the limits to measurement precision. The book is particularly timely because astronomers now have access to a wide range of telescopes on the ground and in orbit. With increasing demand for observing time, it is important to understand the principles and limitations of the instruments and techniques. This book is suitable for undergraduate and graduate students studying observational astronomy. It will provide a ready source of reference for professional astronomers. Physicists and electronic engineers will also find this an absorbing account of the techniques of astronomical observation.