Early Catalogs and Atlases
Hipparchus of Nicaea is credited with the compilation of the first star catalog in 150
©; it contained nearly 850 entries. About ¥ 127, Ptolemy of Alexandria prepared a catalog of 1,022 stars, listing their brightnesses and
positions. He also grouped them in constellations. During the Middle Ages, Muslim astronomers prepared numerous catalogs and planetary tables. These formed the basis for the flowering of European astronomy in the 15th century. About 1590, Tycho Brahe prepared the first modern star catalog, replacing those of Hipparchus and Ptolemy with positions of much greater accuracy.
In 1603, Johann Bayer
published an atlas of Tycho's stars, adding Greek letters for the prominent ones (see constellation). Providing still greater positional accuracy, John Flamsteed, the first astronomer royal of England, produced a catalog of 3,000 stars that was published posthumously in 1725. He numbered the stars in each constellation in order of right ascension (see coordinate systems, astronomy). Many of the brighter stars are still referred to by either their Bayer or their Flamsteed designations.
The Messier catalog of diffuse objects, published in 1771, was compiled by the French astronomer Charles Messier because he grew tired of confusing nebulous objects with the comets he sought. In 1864 the English astronomer John Herschel collected the positions and descriptions of 5,000 diffuse objects. In 1888 the number was increased to 13,000 by the Irish astronomer J. L. E. Dreyer in the New General Catalog. Dreyer also produced two Index Catalogues (IC). Numbers in these catalogs, preceded by M, NGC, and IC, respectively, are in common use today.
One of the most useful sets of stellar catalogs and charts ever prepared is the Bonner Durchmusterung (Bonn Survey 1852Ð59), abbreviated BD. Compiled by Friedrich Argelander at the Bonn Observatory, it contains brightnesses and positions for about 324,000 stars observed with a transit circle. Each star was plotted on the charts with its size proportional to its observed brightness. A southern extension reached to ç22¡. Astronomers in Argentina and South Africa completed the sky coverage with the Cordoba Durchmusterung (CD) and Cape Photographic Durchmusterung (CPD). The numbers in these catalogs are still commonly used to identify stars.
An ambitious program to map the sky, the Carte du Ciel, was initiated in 1889 at an organizational meeting in Paris attended by representatives of 18 observatories. The work began in 1891 but was not completed until 1963. The Carte du Ciel maps, and the Astrographic Catalogs (AC) of the brighter stars covered in this program, remain a major resource, and the program served as a model for future global scientific collaboration. Recently the€ positions have been re-reduced with a modern reference network to give accurate positions for stars as they were approximately 100 years ago. By comparing these positions with recent ones, accurate tangential motions can be derived. Consideration is being given to remeasuring fainter stars on the plates.
Modern Catalogs and Atlases
Examples of important modern catalogs and atlases include the Yale Catalog of Bright Stars, compiled by Dorrit Hoffleit, which contains a wide variety of information on the 9,110 naked-eye stars in the sky; Halton Arp's Atlas of Peculiar Galaxies, devoted to the illustration of a few hundred galaxies having odd structural characteristics (see extragalactic systems); and the Henry Draper Catalogue (HD) of stellar spectra (see Draper, Henry). Begun in 1886, the all-sky portion of the HD catalog was completed in 1924. It contains brightnesses, spectral classes (see Hertzsprung-Russell diagram), and positions for 225,300 stars. Data for 135,683 fainter stars in limited regions were published later (see Harvard classification of stars). The stars in the all-sky catalog are being reclassified from modern plates by Nancy Houk at the University oMichigan. Compilations of specialized information are also available, such as catalogs of variable stars and redshifts of galaxies.
An atlas much used at present is the Palomar Observatory Sky Survey (POSS; see National Geographic SocietyÐPalomar Observatory Sky Survey). It covers two-thirds of the sky and consists of plates taken in the blue and red regions of the spectrum down to about magnitude 20. The southern sky has been covered by similar surveys by the Europeans observing from Chile (blue), and by Australia (red). Several groups have prepared digital versions of the data on these plates. These are available either on the Internet or on CD-ROMs (see compact discs). A repetition of these surveys to brighter limiting magnitudes resulted in the widely used Space Telescope Guide Star Catalog that contains accurate positions and good brightness measures for stars between 6th and 14th magnitude.