Mohr observed the Venus transits of 6 June 1761 and 3 June 1769 and the Mercury transit of 10 November 1769. He also made meteorological observations and measurements of the magnetic declination at Batavia.
After Mohr's death, his observatory was damaged by an earthquake in 1780, fell into ruin and was demolished in 1812.[1]
H.J. Zuidervaart & R.H. van Gent, " "A Bare Outpost of Learned European Culture on the Edge of the Jungles of Java": Johan Maurits Mohr (1716-1775) and the Emergence of Instrumental and Institutional Science in Dutch Colonial Indonesia", Isis: An International Review devoted to the History of Science and its Cultural Influences, 95 (2004), 1-33.