Johann Heinrich Mädler
Overview
Mädler was never officially a full employee of the Observatory but he was effectively used by Encke in such a capacity. He had previously made a considerable number of observations at the private Observatory owned by the Berlin banker, Wilhelm Beer.
By 1830-32 Beer and Mädler had produced the first reasonably good charts of Mars. They had adopted the feature with the current name of Sinus Meridiani as their zero of longitude - today the zero is fixed as the center of a crater called Airy in the Sinus Meridiani ( the craters of Beer and Mädler also lie close to the meridian ). They were the first to report a dark band around the periphery of a shrinking polar cap and also recorded seeing streaks, which could have been the same streaks designated later as 'canali' by Schiaparelli (and misinterpreted as 'canals' by a few other people). The picture below shows their map of 1840.
Herschel had tried to measure the rotation period and his observations were re-worked by Beer and Mädler yielding a period of 24 hours 37 minutes 23.7 seconds, which is only one second in error ( should be 22.6 seconds ).
During 1834-6, Beer and Mädler published their Mappa Selenographica ( Der Mond nach seinen kosmischen und individuellen Verhältnissen oder allgemeine vergleichende Selenographie ), one of the best moon maps to appear until then (held by many to remain unsurpassed until 1878), and Der Mond (1837) , a classic on lunar research.
Both astronomers are mentioned briefly in Jules Verne's work 'From the Earth to the Moon'.
In 1836, Encke appointed Mädler as an observer at the Berlin Observatory, and here he continued his work on planets, and also studied double stars. In 1840 he moved to Dorpat as director of the Observatory.
