Illustration of the German-British astronomers William Herschel (1738-1822) and his sister Caroline Herschel (1750-1848) making observations with his 40-foot telescope. William constructed several telescopes and used them to extensively study the night sky. He catalogued double stars and studied the Moon's surface, but is remembered most for his discovery of Uranus in 1781. He also discovered two satellites of Uranus (Titania and Oberon) and two of Saturn (Mimas and Enceladus). Caroline helped to prepare his catalogues and reports. She found 8 new comets between 1786-97, 3 new nebulae in 1783 and revised Flamsteed's star catalogues to make it easier to use.