New updated edition. A general guide to astronomy; some say it should be called the Astronomical Treasury. Same large page-size format as the Astronomical Calendar. The Companion begins with an "Overview of Astronomy" and pictures that make it easy to understand coordinate systems and orientation in space. A strand running through the book is the series of 30 ten-inch-diameter diagrams showing expanding spheres of space, from the Moon's orbit and the domains of planets and comets out through the nearest stars, the neighboring regions of our Milky Way galaxy, the whole galaxy, the local group of galaxies, the Virgo cloud, and so on to the eerie limits of the universe. Among many other features: a map and catalogue of star names with their derivations; the seasons (including their linking with traditional dates such as Beltane, Halloween, St. Lucy's Day); the world's calendars; precession and its many consequences; "Moonlight" and "Earthlight" and "Moon as Signpost"; comparative distances; a comprehensive Hertzsprung-Russell Diagram (the graph that relates all the kinds of star by color and brightness); and pages on constellations, meteor showers, double stars, variable stars, even cloudiness by month and region.