Herschel telescope, artwork. This is a plan for one of more than 400 telescopes designed by the German-born British astronomer William Herschel (1738-1822). The telescope itself is seen in R102/175. This model is similar in size and design to the 10-foot telescope (R102/174), which had a 3-metre-long tube. Other models were the 7-foot, 20-foot and 40-foot telescopes. This one is mounted on a wheeled frame, and various mechanisms allow the angle to be adjusted as needed. The observer would use a ladder to make observations by looking down an eyepiece on the side of the tube (upper left) at an image that was projected to the side by the primary mirror in the base of the tube. The mirror was made of polished metal, instead of glass. Herschel's discoveries included Uranus (1781) and several moons of Saturn and Uranus.