Celestial Sphere

Abstract

Man’s imagination has from ancient times made star-pictures out of easily recognizable groupings of stars (Fig. 2.1). In the northern sky we easily recognize the Great Bear (Plough). We find the Polestar if we produce the line joining the two brightest stars of the Great Bear by about five times its length. The Polestar is the brightest star in the Little Bear; if we extend the line past it to about the same distance on the other side, we come to the “W” of Cassiopeia. With the help of a celestial globe or a star-map, other constellations are easily found. In 1603, J. Bayer in his Uranometria novadenoted the stars in each constellation in a generally decreasing order of brightness as α, β, γ …. Nowadays these Greek letters are supplemented by the numbering introduced by the first Astronomer Royal,J. Flamsteed,in his Historia Coelestis Britannica(1725).The Latin names of the constellations are usually abbreviated to three letters.KeywordsGeographical LatitudeBright StarSidereal TimeGeographical LongitudeCelestial PoleThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.