In 1781 the amateur astronomer Herschel identified Uranus, the first planet to be discovered since Antiquity. He was appointed court astronomer to George III the following year, 1782. Working with his sister Caroline (1750–1848), whom he had trained, he made four complete surveys of the night sky and was the first person correctly to describe the Milky Way. Using his great forty-foot telescope constructed over four years, he found two new satellites of Saturn in 1789. Herschel's discoveries astonished the public and inspired Romantic writers like Blake, Byron and Keats. He discovered more than two thousand nebulae and over eight hundred double stars.Herschel sat for this portrait on the encouragement of his friend, the naturalist, Sir William Watson: 'When you are in town on full moon nights you may perhaps spare an hour early in the morning, & may sit three or four times running – & the thing may in this way be done without much inconvenience or loss of time'.