In some 4,000 concise, up-to-date entries, this dictionary cuts a clear path through the maze of complex technical language, offering full, clear definitions drawn from all aspects of astronomy. Here are succinct definitions for the Big Bang theory, comets, eclipses, Magellanic Clouds, Mars, quasar, relativity, and variable stars. Entries on telescopes and other measuring devices, observatories, space missions, and recently named Solar System objects show how astronomers have explored the universe. The Dictionary also provides biographical entries on eminent astronomers from Copernicus to Edwin Hubble. A Dictionary of Astronomy opens a window on the universe for amateur astronomers everywhere.