13 Mayer, Tobias (1723-1762).Opera inedita. -- Göttingen: Johann. Christian. Dieterich, 1775.
After Mayer's untimely death, George Christoph Lichtenberg undertook to edit some of Mayer's papers for publication, among them the smaller moon map of 1750. To engrave it, he selected Joel Paul Kaltenhofer, who was not only one of the best engravers in Germany, but a friend of Mayer, and himself a skilled lunar artist. Kaltenhofer's first attempt was rejected, but the second proved satisfactory.
One unusual feature of the map is that it has north at the top, contrary to the tradition inaugurated by Cassini and continued by every other lunar map until 1960. When Schröter incorporated Mayer's map in his own moon book (item 14), he took exception to this disregard of convention, and had the map re-engraved with south up.
The Mayer map was the first to be based on micrometric measurements. However, the printed coordinate system, the first on a lunar map, did not appear on Mayer's original map--it was added by Kaltenhofer, at the editor's request. The detail of the lunar highlands shows Mare Nubium (Sea of Clouds) at the left, the craters Ptolemy and Alphonsus just above center, and Hipparchus and Albategnius parallel to them at right.