The aim of this book is to bridge the gap between the pure instrumental physicist and the user of detectors and spectrometers. The essential parameters describing the performance of these devices are identified and the designs of a wide variety of practical instruments are illustrated working on topical problems. The author has spent 14 years designing and applying spectrometers in the visible and near infra-red domains predominantly to investigate gaseous nebulae. Most recently he has designed for instance a large (15 x IS-in.) Ha interference filter for the SRC, 48-in. Schmidt camera,...