The following year, frustrated with the performance of his telescopes, William set about designing and manufacturing his own equipment. Building a telescope was a team effort, with many components coming from a variety of sources. Eyepieces, micrometers, tubes and other parts required the work of skilled craftsmen.
The metal mirrors required intense polishing, as large glass mirrors were not yet available at that time. In her memoirs, Caroline recalled William’s involvement in this task. “I spent so much of my time copying music and practicing, as well as taking care of my brother when he was polishing. To keep him alive, I sometimes even had to feed him by putting food in pieces in his mouth,” she wrote. “This was particularly the case when he was in charge of finishing a 2 meter mirror. He hadn’t let go for 16 straight hours. By the end of 1779, after verification of his designs, William was considered the greatest telescope maker of his time.
Two years later, while studying double stars (two stars that appear close to each other when viewed from Earth), William noticed for several nights a faint object moving slowly through compared to background stars, and which he first thought was a comet. However, after further study and confirmation from his colleagues, it turned out that he had discovered a planet: one of the ice giants of the solar system. He named it Georgium Sidus, “George’s Star” in Latin, in honor of King George III. Naming the new planet after the British monarch, however, drew criticism in other countries, so William eventually opted for Uranusin reference to the god of the sky from Greek mythology.
Visible to the naked eye, Jupiter, Saturn and the inner planets of the solar system have been known for millennia. Uranus was the first planet discovered using a telescope. William won international acclaim for his discovery. He was knighted and appointed court astronomer by the king, and granted an annual pension of £200, provided he lived near Windsor and was available whenever the king wished to observe the stars.