A comprehensive account of the modern instruments and techniques used in astronomy and astrophysics. Drawing together an ever-diverging array of observational techniques, using the common thread of detection-imaging-ancillary instruments pattern, the book provides a unified view of astrophysical investigation. The text starts form first principles and explains each method up to the point at which the reader can begin practical work with the equipment and even start designing it. Exercises with answers are used to reinforce the ideas presented in each chapter.