BAYER, Johann.

An excellent copy, the plates in clean, clear impression, of the second edition of Bayer’s stunning and most influential star atlas, comprising 51 engraved celestial plates. First printed in 1603, this is considered the most complete catalogue of pre-telescopic astronomy.

Johann Bayer (1572-1625) was a German lawyer of Rain (Bavaria), who graduated at Ingolstadt and became legal adviser to the city council of Augsburg. Among his many interests were archaeology and mathematics, but his true passion was astronomy and particularly studying the location of stars in the sky. Bayer is today most known for his activity as uranographer (celestial cartographer) and for his “Uranometria” (here). This work illustrates over 2,000 stars, many more than any previously published atlas. The main source of data regarding the stars’ position was a recently published catalogue by the Danish astronomer Tycho Brahe (1546-1601), to which Bayer added c. 1000 stars from the Almagest and his own observations.

Remarkably, here Bayer “introduced the convention of labelling bright stars by Greek letters, a system that astronomers still use. They are now commonly termed Bayer letters. For example, on this scheme the bright star Betelgeuse is also known as Alpha (α) Orionis, meaning Alpha of Orion […]. Contrary to popular belief Bayer did not letter the stars in strict order of brightness – in fact, magnitude estimates at that time were not good enough for this to have been possible. What he actually did was to group the stars into magnitude classes, from first to sixth, then allocated letters to the members of each class as he saw fit.” (Ridpath).

The exquisitely engraved plates were realised by the German engraver Alexander Mair (c.1559– c.1620) on the basis of drawings made by the Dutch painter Jacob de Gheyn (1565-1629); they have been defined “a true work of art” (Ridpath). There are 48 plates depicting Ptolemaic constellations, followed by, in plate 49, the first representation of the southern sky, depicting 12 new constellations first observed by Dutch navigators Pieter Keyser and Friedrich de Houtman during a voyage to the East Indies in 1595. Constellations are always presented with the traditional mythologic outlines, but they are also placed in a carefully engraved coordinate system grid of longitude and latitude. The two final charts are planispheres, respectively illustrating the northern and southern celestial hemispheres.

Due to its completeness and artistic quality, Bayer’s atlas became highly popular and it was reprinted eight times between 1648 and 1689. A remarkable feature of the second edition (here) is the improved readability of the plates. In the first, tables of the stars were printed on the back of each chart, but the lettering showed through the page spoiling the beauty of the illustrations. For this reason, the tables were removed from all subsequent editions and printed as a separate star catalogue titled ‘Explicatio characterum aeneis Uranometrias’ (1624).

The ex libris on the fly likely belongs to Samuel Eglinger (1638-1673), a mathematician and doctor active in Basle and author of a few medical works. The other early calligraphic inscription reads “C”, possibly the initial of the name or title of another owner, and “ab Hettlingen”, meaning from Hettlingen, a city in Switzerland located not too far from Basle.