This book presents a comprehensive guide to the impact of the internet on professional astronomy. Each chapter deals with a range of the electromagnetic spectrum, with authors first discussing the corresponding problems for each range, particularly those that can be treated by access to very large databases. They then describe how data and information can be found on the internet, and explain how to access and process this information. This is complemented by a detailed guide to astronomy on the internet, including several hundred links of interest to internet resources, arranged by topic. The book gives examples of the analysis of data from telescopes such as the Hubble Space Telescope, with a step-by-step guide to using such data. Written by experts from all over the world, this book will be of interest to all astronomers, both professional and amateur, and provides a key to the high-tech work of modern astrophysics.