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Fine example of the map of the Constellation Aquila, from Bayer's Uranometria.

Includes early hand-written notes in the margins, locating the neighboring constellations.

Perhaps the most illustrious of all celestial atlases is Bayer's Uranometria, the forerunner of all star atlases which contained 51 star charts, of which 48 were Ptolemaic constellations. Each plate has a carefully engraved grid, so that star positions can be read off to fractions of a degree. These positions were taken from the catalog of Tycho Brahe, which had circulated in manuscript in the 1590s, but which was only printed in 1602.

Another important feature of the atlas was the introduction of a new system of stellar nomenclature. Bayer assigned Greek letters to the brighter stars, generally in the order of magnitude, so that the bright star in the Bull's eye became alpha Tauri (and the brightest star in the Centaur became our familiar alpha Centauri.) These letters were placed on the charts themselves, and also on a table that accompanied each chart.

Aquila, the Eagle, is an ancient constellation whose history is linked to the Greek gods. The most often-told story is that of Hebe, daughter of Zeus and Hera, who married Heracles. Before her marriage Hebe was the goddess of youth and she appeared in ceremonies as the official cup bearer (i.e., in religious functions, she was responsible for pouring the wine). She gave up the post after her marriage (although some accounts say that in one ceremony, she indelicately exposed herself and was promptly terminated). In any case, the position was open, and Zeus sought a suitable replacement. Ganymede, a splendid Trojan prince, was Zeus's eventual choice. Zeus either disguised himself as an eagle or sent his Royal Eagle. Ganymede was plucked from his native land and taken to Mount Olympus where he became the wine-pourer for all the gods.

This explains why Ganymede is Jupiter's brightest and largest companion: Jupiter of course being the Roman name for Zeus. The constellation Aquila is supposed to represent the eagle carrying away the youth. There are four or five fairly bright stars just below the asterism which are meant to represent the boy (this asterism is called "Antinous" but is not recognized any longer). Eventually Zeus put Ganymede's own image in the skies, as the god's water bearer, Aquarius.