Zenith sector telescope, 1727 (iron, tin)

Creator: George Graham This zenith sector telescope was constructed by George Graham in 1727 for Bradley's personal use in studying the parallax of the star Gamma Draconis following work he had begun on the detection of parallax at Kew with Samuel Molyneux. When he was appointed third Astronomer Royal in 1742, Bradley only agreed to bring this instrument to Greenwich after the Government paid him the princely sum of £45 for it. With it he discovered two major phenomena: the aberration of light and the nutation (wobbling) of the Earth's axis. It was used at Greenwich until 1837. It was then used at the Observatory at the Cape of Good Hope between 1837 and 1839.