General-Karte der sichtbaren Seite der Mond-oberflaeche zugleich als Übersichts-Blatt zur grössern Mondkarte von Wilh. Beer und Joh: Heinr. Mädler.

An early representation of the viewable surface of the moon by Johann Heinrich Mädler (1794-1874) and Wilhelm Beer (1797-1850).

Ignoring the occasional pre-telescopic appearance of exceptionally large sunspots, the Moon is the only heavenly body which shows features to the naked eye--the Man in the Moon. These features are permanent, and it was therefore obvious that the Moon always keeps its same face turned to us (although there are minor perturbations that were not noticed until later).
In 1830, the astronomer Mädler teamed up with Wilhelm Beer, a Berlin banker, to produce their renowned lunar map.
Johann Heinrich von Mädler ( 1794 -1874) is one of the most important German astronomer's of the late 19th century. Madler began giving academic lessons as a private tutor and in this way met Wilhelm Beer, a wealthy banker in 1824. In 1829, Beer decided to set up a private observatory with a 95 mm refractor telescope made by Joseph von Fraunhofer, when Mädler would find his earliest work as an Astronomer.
In 1830, Madler and Beer began producing drawings of Mars which later became the first true maps of that planet.
Madler and Beer also produced the first exact map of the Moon, Mappa Selenographica, published in four volumes in 1834–1836. In 1837, their description of the Moon (Der Mond) was published. Both were the best descriptions of the Moon for many decades, not superseded until the map of Johann Friedrich Julius Schmidt in the 1870s.
Beer and Mädler drew the firm conclusion that the features on the Moon do not change, and there is no atmosphere or water. In 1836, Johann Franz Encke appointed Mädler an observer at the Berlin Observatory. In 1840, Mädler was appointed director of the Dorpat (Tartu) Observatory in Estonia, succeeding Friedrich Wilhelm Struve who had moved to Pulkovo Observatory. He carried out meteorological as well as astronomical observations. He continued Struve's observations of double stars. He remained in Tartu until he retired in 1865, and then returned to Germany.