This book is based on a required course for graduate students in Astronomy which I taught for a number of years at the University of Illinois. The premise of the course is that both theoretical astronomers and observers should have a basic understanding of the techniques of observational astronomy. The emphasis is on the underlying physics of the methods of detection and analytical tools (statistical and otherwise) that astronomers find useful. The great variety of current instruments and the rapid introduction of new instruments preclude an in-depth treatment of the peculiarities and idiosyncrasies of many instruments. But every instrument has its own idiosyncrasies and its own ways of corrupting the data and deceiving the observer. The topics in this book, I believe, cover the minimum which is required of anyone attempting to understand or interpret observational astronomy data.

Throughout the book equations are given in mks (SI) units so that it is easy to relate the discussion to practical quantities such as volts and watts. This is true even in the chapter on gravitational waves, a subject for which many texts and references use geometrized units (c = 1, G = 1). I prefer to keep c and G around rather than having to figure out where to put them when I need to calculate power. I also like being able to check equations using dimensional analysis. In the text other units are freely worked in.