(1794-1874), Astronomer

Johann Heinrich Mädler was born in Berlin, Germany on 29 May 1794. After graduating from the Gymnasium, Mädler became, at the age of twenty-three, a seminary teacher in Berlin. His interest in astronomy had been awakened by the appearance of the comet of 1811, but he did not have an opportunity to make extensive astronomical observations until he met the rich Berlin banker Wilhelm Beer. Beer maintained a private observatory in Berlin; and he and Mädler worked there together, mainly on lunar topography. In making their observations they used a Fraunhofer telescope with an aperture of 95 millimetres.

Their joint publications gave such a favorable impression of Mädler’ abilities that, beginning in 1836, he was an observer at the Berlin observatory, then directed by Encke. Here too he worked on the topography of the moon and the planets, chiefly Mars. The most important achievement from his collaboration with Beer was undoubtedly a map of the moon and accompanying two-volume text: Der Mond nach seinen kosmischen und individuellen Verhältniseen(1837). The lunar map (with a diameter of 97.5 centimetres) is in many respects the equal of Lohrmann’s representation.

In 1840 Mädler accepted an offer from the observatory at Dorpat; he also obtained a professorship and began to publish his considerable body of work.

Mädler was also a pioneer popularizer of astronomy. After giving popular scientific lectures, in 1841 he published Populäre Astronomie, which went through six editions during his lifetime. He also contributed to the dissemination of astronomical knowledge through articles in journals and newspapers. In 1888–1889—with the active cooperation of Wilhelm Foerster—the popular astronomy movement established its own institution in Berlin (the Urania Observatory); and today there is a large network of popular astronomy journals published throughout the world.

In Populäre Astronomie, Mädler had briefly sketched the history of astronomy. Following his departure from Dorpat (1865) and return to Germany, he devoted himself to this subject. The result of his labour, the two-volume Geschichte der Himmelskunde (1873), contains an extraordinary treasure of valuable historical data that Mädler had been gathering for decades. Mädler died in Hannover, Germany on 14 March 1874.