ASTRONOMICAL MAP

any cartographic representation of the stars, galaxies, or surfaces of the planets and the Moon. Modern maps of this kind are based on a coordinate system analogous to geographic latitude and longitude. In most modern cases, they are compiled from photographic observations made either with Earth-based equipment or with instruments carried aboard spacecraft. Representations of the celestial regions have long been used for both navigational and scientific purposes. The earliest versions consisted of charts, globes, and drawings that grouped stars apparently close together in the sky into constellations, imaginative configurations of bright stellar bodies named after legendary or mythological beings that they supposedly resembled in form. Classical Greek astronomers are known to have employed maps and globes depicting constellations, but no examples survive. The ancient tradition was followed by the Alexandrian astronomer Ptolemy (fl. AD 127145) in compiling his Almagest, which provides magnitudes and ecliptic coordinates for 1,022 stars grouped into 48 constellations. For the next 1,400 years or so, Islamic and European astronomers relied heavily on Ptolemy, basing their star catalogs and astronomical tables on his work. Other astronomical reference systems were developed independently in early antiquity, as exemplified by the lunar mansions, which are 28 divisions of the sky devised in China and India, and the Egyptian decans, which consisted of 36 star configurations circling the sky to the south of the ecliptic. The system that is used by modern astronomers, however, has grown out of that originally established by Ptolemy. Because no attempts were made in medieval Europe to refine or add to the existing information on the ancient constellations, the star maps produced during this period were based almost wholly on the Ptolemaic star catalog. The renaissance in science and the development of printing led to widespread publication of astronomical maps, globes, and books from the late 15th and 16th centuries onward throughout much of Europe. The first important printed star maps were published in 1515 by the German painter and printmaker Albrecht Drer. These maps consisted of two planispheres that depicted the classical constellation figures. Alessandro Piccolomini's De Le Stelle Fisse Libro Uno (1540) constituted the first book of printed star charts (as opposed to mere pictures of constellations) and introduced a lettering system for the stars. The star atlas published by Giovanni Paolo Gallucci in 1588 was the first to include coordinates. Only the 48 constellations listed in the Almagest were included in star charts produced until the end of the 1500s. Since that time 40 additional constellations, most notably those visible in the Southern Hemisphere, were introduced in celestial globes and star atlases. A definitive list of 88 constellations was established, and the boundaries of these star groupings fixed in 1930 by the International Astronomical Union. The idea of a photographic atlas of the entire sky was proposed as early as 1887, but it was not until 1914 that such a project was completed. This effort, the Franklin-Adams Charts, consisted of 206 prints of stars with a limiting photographic magnitude of 15. Improved equipment and techniques for photographic mapping of the skies have yielded various star atlases of superior quality since the early 1950s. Among these are the National Geographic Society-Palomar Observatory Sky Survey and Norton's Star Atlas. Since the 1960s, Earth-orbiting astronomical observatories, immense radio telescopes, electronic detection apparatus (e.g., the charge-coupled device and charge-intensified device ), and computerized image processing have enabled astronomers to prepare extremely accurate and highly detailed atlases of galaxies and catalogs of cosmic sources of infrared, radio, and X-ray emissions. In addition, detailed relief maps of the Moon and the inner planetsMercury, Venus, and Marshave been produced with the aid of high-resolution photographs and radar observations. any cartographic representation of the stars, galaxies, or surfaces of the planets and the Moon. Modern maps of this kind are based on a coordinate system analagous to geographic latitude and longitude. In most cases, modern maps are compiled from photographic observations made either with Earth-based equipment or with instruments carried aboard spacecraft. Additional reading Richard Hinckley Allen, Star-Names and Their Meanings (1899, reprinted as Star Names: Their Lore and Meaning, 1963), a classic compendium; for a more trustworthy treatment of Arabic names, see Paul Kunitzsch, Arabische Sternnamen in Europa (1959). Deborah J. Warner, The Sky Explored: Celestial Cartography, 15001800 (1979), provides a historical overview. Joseph Needham, Science and Civilisation in China, vol. 3, Mathematics and the Sciences of the Heavens and the Earth (1959); and Knut Lundmark, Luminosities, Colours, Diameters, Densities, Masses of the Stars, ch. 4 in Handbuch der Astrophysik, vol. 5 (193233), pp. 210697 (with a sizable appendix), are both far more germane to astronomical maps than their titles imply. Information on types of star catalogs and classification systems may be found in Star Catalogues, ch. 6 in Ivan I. Mueller, Spherical and Practical Astronomy (1969). Practical catalogs and atlases include Dorrit Hoffleit, The Bright Star Catalogue, 4th rev. ed. (1982), with data compiled through 1979 (supplement published in 1983); Donald H. Menzel and Jay M. Pasachoff, A Field Guide to the Stars and Planets, 2nd ed., rev. and enl. (1983); and Ian Ridpath, Universe Guide to Stars and Planets (1985). Owen Gingerich Warren Melvin Young