Charles Green (astronomer) - Career in Astronomy

Career in Astronomy

Green was appointed as Assistant to the Astronomer Royal, James Bradley, succeeding the astronomer Charles Mason who left to join the expedition to the Cape of Good Hope to observe the 1761 transit of Venus. Following Bradley's death in 1762, Green continued in the role of assistant for Bradley's successor Nathaniel Bliss. Due to the ill-health of Bliss, much of the work of practical observational astronomy devolved upon Green at this time.

In 1763, Green, along with the astronomer Nevil Maskelyne, was instructed by the Board of Longitude to make the voyage to Barbados to act as monitors of the test of John Harrison's H4 chronometer, which was in the running for the Longitude Prize, the prize offered by the British Government for the devisor of an accurate method of determining the longitude of a ship at sea. Their duties, after they arrived in Barbados and were awaiting the chronometer's arrival on another ship, involved determining the local longitude by observation of the Galilean moons of Jupiter to determine the local longitude, and after the arrival of the mechanism which was in the care of Harrison's son William, the comparison of the results of the chronometer with their astronomical observations to judge the mechanism's accuracy. On the voyage to Barbados, the pair were also using their observations to determine the accuracy of the lunar distance method, Maskelyne's own method of calculating the longitude of a ship at sea. An argument ensued between Maskelyne and William Harrison, which dragged in Green, as Harrison was of the opinion that Maskelyne was not an impartial observer and was a rival of his father in the pursuit of the Longitude Prize. A compromise was reached in which the monitoring of the Harrison mechanism was undertaken by Maskelyne and Green on alternate days.

Green's return to England in the autumn of 1764 coincided with the death of Nathaniel Bliss; Green returned to Greenwich to continue Bliss' work until the appointment of a new Astronomer Royal. The new Astronomer Royal proved to be Nevil Maskelyne. Green briefly served under him as assistant, but left Greenwich after a disagreement with his new superior. Wales' account says that Green was involved in a survey to determine the feasibility of transporting water from the River Colne to provide water to Marylebone in London, although Green's survey confirmed the fears of mill owners downstream that the canal would result in a failure of the water supply needed for their operations and led to the scheme being dropped. Although this is unmentioned in Wales's short biography, Green is recorded as being the purser on the HMS Aurora in 1768. In that same year, the Royal Society appointed him to accompany James Cook's voyage to observe the 1769 transit of Venus; despite their earlier disagreement, Maskelyne who was serving on the Society's Transit of Venus Committee recommended his former assistant for the post.