"First published in 1910, coinciding with the first of two appearances by Halley's Comet during the book's life, Norton's owes much of its legendary success to its unique maps, arranged in slices known as gores, each covering approximately one-fifth of the sky. Every star visible to the naked eye under the clearest skies - down to magnitude 6.5 - is charted along with star clusters, nebulae and galaxies. Extensive tables of data on interesting objects for observation accompany each of the precision drawn maps. Preceding the maps is the unique and authoritative reference handbook covering time-keeping and positional measurements on the celestial sphere; the Sun, Moon and other bodies of the Solar System; telescopes and other equipment for observing and imaging the sky; and stars, nebulae and galaxies. Throughout, succinct fundamental principles and practical tips guide the reader into the night sky. The appendices Units and Notation, Astronomical Constants, Symbols and Abbreviations, and Useful Addresses complete what has long been the only essential reference for the stargazer." "Now presented more accessibly than ever before, the text and tables of the 20th edition have been revised and updated to take account of the new and exciting developments in our observation of the cosmos. The redesigned star maps offer outstanding legibility, in the living room or under a red light in the dark outdoors."--BOOK JACKET.