Today's professional astronomers must be able to adapt to use telescopes and interpret data of all wavelengths. The Cambridge Observing Handbooks for Research Astronomers is designed to provide them with a series of concise, self-contained handbooks which cover the basic principles peculiar to observing in a particular spectral region, or to using a particular technique or type of instrument. The books can be used as an introduction to the subject, and as a handy reference - for use at the telescope, or in the office. They also promote an understanding of other disciplines in astronomy and a modern, multi-wavelength, multi-technique approach to research. Although aimed primarily at graduate students and researchers, many titles in the series will be of interest to keen amateurs and undergraduate students.