BAYER'S URANOMETRIA IN FACSIMILE Uranometria von Johann Bayer 1603. Edited by Ulrich Schaake and Winfried Berberich (Kunstschatzeverlag, Gerschsheim, 2010). Pp. [112]. ISBN 9783-934223-35-6. Die Himmelsvermessung des Johannes Bayer. Jurgen Hamel (Kunstschatzeverlag, Gerschsheim, 2010). Pp. 176. ISBN 978-3-934223-36-3. euro178 for the two vols.How can we keep track of the stars? How do we know which one is which?In our age of setting circles, go-to telescopes, and digital catalogues, this may well seem an otiose question. But what about Antiquity or the Middle Ages? We tend to forget that the sky contains no visible coordinate grid. Clearly some sort of pattern recognition scheme was essential, and here the mythological figures and their anatomy served as a brilliant mnemonic device for the ancient Greek and Babylonian worlds. Ptolemy framed the stars both with an imagined coordinate system and a carefully described but equally imagined parade of memorable persons and animals. [T]he descriptions we have applied to the individual stars as parts of the constellation are not every case the same as those of our predecessors, Ptolemy wrote (Toomer, 1984, 340); in many cases our descriptions are different because they seemed to be more natural and to give a better proportioned outline to the figures described. Thus, for instance, those stars which Hipparchus places 'on the shoulders of Virgo' we describe as 'on her sides'. Ptolemy's descriptions became the gold standard for identifying stars. Translated from Greek into Arabic they gave the names we use today for some of the stars: Algol, Aldebaran, Altair, Deneb, Fomalhaut, and others.The next major step was to prepare charts not only with the fabled figures drawn to match Ptolemy's descriptions, but also to include some kind of short label to designate each star. Johannes Bayer was not the first to try this, but his Limnometria of 1603 with its handsomely engraved figures and Greek letter tags on 5 1 conveniently sized plates so greatly outstripped the prior attempts that his atlas became the formative pioneer celestial cartography. His plates were used repeatedly for subsequent editions throughout the seventeenth century, and by 1661 had been retouched to renew the clarity of the impressions.Now a further edition, a precise photographic facsimile, has become available. It duplicates the scale of the original plates very accurately, and the contrast the reproduction has been well controlled to bring out the delicacy of the original engravings. The format is generous so the plates are not folded, and on each facing page appears the text, which the original 1603 edition was inconveniently placed on the back of each chart. …