The Constellations of
Johann Bayer

German amateur astronomer Johann Bayer (1572-1625) published the first all-sky atlas, Uranometria, in 1603.  Bayer developed the now common practice of labeling stars in descending order of their brightness using Greek letters; that is, Alpha being the brightest, Beta second brightest, and so on.  If a constellation has more stars than Greek letter, Roman letters are then used after the Greek letters have been exhausted.  Bayer added 12 constellations to the sky from the "amorphae" or formless stars left over after the classical constellations were defined.

Many of Bayer's constellations can be, at least in part, attributed to the Dutch navigator P.D. Keyser who identified several star groups as navigation aids several years in advance of the Uranometria.