   charles mason (oakridge lynch, near stroud, gloucestershire, april 1728&nbsp;&ndash; philadelphia, october 25, 1786) was an english astronomer who made significant contributions to 18th-century science and american history, particularly through his involvement with the survey of the mason-dixon line, which came to mark the border between maryland and pennsylvania (1764â1768). ==early career== mason's early career was spent at the royal greenwich observatory near london. he served as assistant astronomer from 1756 to 1760 under the reverend james bradley, the astronomer royal. while employed at the greenwich observatory, mason became familiar with professor tobias mayerâs tables of the moon. the lunar tables were designed to solve the problem of determining longitude at sea, a challenge that frustrated scientists and navigators for decades. mason worked throughout his life to perfect the lunar tables as a method of improving navigation at sea. in 1787, mason was awarded Â£750 by the board of longitude for his work on perfecting the tables.cope, thomas d. and h. w. robinson. "charles mason, jeremiah dixon and the royal society." notes and records of the royal society of london. vol 9, no 7, 1951. p 75. ==1761 transit of venus== in 1761, mason was assigned to travel to the island of sumatra to observe the transit of venus as part of an international effort to record data that would enable scientists to determine the distance from the earth to the sun. mason was joined by jeremiah dixon, a surveyor and amateur astronomer from cockfield in the county of durham. owing to an attack by a french man-of-war, they did not reach their destination in time for the transit and were forced to record their observations from the cape of good hope. on the way back from the cape they visited st. helena where they made a series of observations with the astronomer nevil maskelyne. ==the masonâdixon line survey== thumb|" a plan of the west line or parallel of latitude" by charles mason, 1768 from november 1763 to 1768, mason and jeremiah dixon established the boundary line between the american provin
1728_births 1786_deaths Burials_at_Christ_Church_(Philadelphia) English_astronomers English_surveyors Pennsylvania_colonial_people People_from_Stroud