Star Atlases, Constellations, and Celestial Nomenclature

Star maps and atlases are used to navigate the heavens and learn the names of constellations and the celestial objects that reside in each one. Star atlases use specific symbols to denote the various types of celestial objects. Stars are denoted by dots—the larger the dot, the brighter the star that is plotted on the atlas. Similar to terrestrial atlases, star atlases contain lines that run north-south and east-west to provide position coordinates. The north-south lines are called right ascension, while the east-west lines are called declination. Paper star atlases are printed for an epoch such as the year 1950 or 2000. Electronic star atlases have become very popular, almost replacing paper atlases. They have the advantage of producing displays for any epoch, for any image scale, and can plot millions of stars and other celestial objects. Besides providing star charts, celestial software can also show simulations such as the motion of planets or eclipses. The same software can be used to control telescopes to point them toward an object selected from the atlas.