Mayer Tobias (1723-1762).

Bericht von den Mondskugeln. – Nuremberg: Zu finden in der Homännischen Officin, 1750.

Mayer introduced the revolutionary idea of using a micrometer within the telescope to determine the exact positions of the lunar features. He began his lunar studies in 1748 and made at least 40 detailed drawings of various regions, from which he planned to construct both a lunar map and a lunar globe. In 1750 the Cosmographical Society of Nuremberg issued a prospectus for the globe, which included two plates, made from Mayer's drawings, to demonstrate the quality of his observations. The lunar globe was never produced, as the publisher flirted with bankruptcy, and Mayer became involved in other projects. But his two lunar maps and his careful drawings were eventually published (see the Mayer 1775 and 1881 illustrations).

This plate, which shows the region in the lunar highlands around Scheiner and Longomontanus, is remarkable for two reasons. First, it is a mezzotint, the first time this technique was used for a lunar map (if we except a tiny text engraving of the crater Plato by Bianchini in 1728). Second, the engraver failed to reverse the drawing, and so the craters which appear here on the left of the terminator should actually lie on the right. As the caption belatedly explains: "If you want to view the print correctly, you must hold it up to a mirror." Image source: Mayer, Tobias, and Johann Michael Franz. Bericht von den Mondskugeln. Nüremberg: Zu finden in der Homännischen Officin, 1750, pl. 2.

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Opera inedita. – Göttingen: Johann. Christian. Dieterich, 1775.

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. Image source: Mayer, Tobias, and Georg Christoph Lichtenberg. Opera inedita. Vol. 1, Gottingen: Johann. Christian. Dieterich, 1775, frontispiece.

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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 10), he took exception to this disregard of convention, and had the map re-engraved with south up.