Charles Green (baptised 26 December 1734 – 29 January 1771) was a British astronomer, noted for his assignment by the Royal Society in 1768 to the expedition sent to the Pacific Ocean in order to observe the transit of Venus aboard James Cook's Endeavour. Early life and education Born sometime in December 1734, Green was the youngest son of Joshua Green, a prosperous farmer who lived near Swinton in Yorkshire. His education, according to his future brother-in-law William Wales, was chiefly at a school near Denmark Street in Soho, London. This school was run by his eldest brother, the clergyman Rev. John Green, and the younger Green went on to become an assistant teacher there, continuing his studies in astronomy until he joined the staff of the Royal Greenwich Observatory in 1760. 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 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