Johann Heinrich von Mädler (May 29, 1794 - March 14, 1874) was a German astronomer. In 1829 Wilhelm Beer, a wealthy banker, decided to set up a private observatory with a 95 mm refractor telescope made by Joseph von Fraunhofer, and Mädler worked there. In 1830 they began producing drawings of Mars which later became the first true maps of that planet. They were the first to choose what is today known as Sinus Meridiani as the prime meridian for Mars maps. Read more