From 1808, he was adjunct professor of astronomy in Copenhagen. He directed the Mannheim observatory from 1813 to 1815, and then in 1815 was appointed Professor of Astronomy in Copenhagen and Director of the Observatory.[2]
From 1817 he directed the triangulation of Holstein, to which a few years later was added a complete geodetic survey of Denmark (finished after his death). For the sake of the survey, Schumacher established the Altona Observatory at Altona, and resided there permanently.[2] He cooperated with Carl Friedrich Gauss for the baseline measurement (Braak Base Line) in the village Braak near Hamburg in 1820.
He died in Altona on 28 December 1850. He was buried in the Heilig Geist Kirchhof (Holy Ghost Church) in Altona. The site is now marked by a stone memorial.
Family
In 1812 he married Christine Madelaine Schoon.
Their son, Richard Schumacher (1827–1902), was his assistant from 1844 to 1850 at the conservatory at Altona. Having become assistant to Carlos Guillermo Moesta (1825–1884), director of the observatory at Santiago de Chile, in 1859, he was associated with the Chilean geodesic survey in 1864. Returning in 1869, he was appointed assistant astronomer at Altona in 1873, and afterwards at Kiel.[2]