History of the telescope
The earliest known telescope appeared in 1608 in the Netherlands when an eyeglass maker named Hans Lippershey tried to obtain a patent on one. Although Lippershey did not receive his patent, news of the new invention soon spread across Europe. The design of these early refracting telescopes consisted of a convex objective lens and a concave eyepiece. Galileo improved on this design the following year and applied it to astronomy. In 1611, Johannes Kepler described how a far more useful telescope could be made with a convex objective lens and a convex eyepiece lens and by 1655 astronomers such as Christiaan Huygens were building powerful but unwieldy Keplerian telescopes with compound eyepieces.
Newton's reflector
Newton's third telescope was built in 1671-1672 by Newton and his "chamber fellow" at Trinity College John Wickins. He reported that Wickins did a better job of figuring the mirror than he had done on his second telescope. This is the telescope that he had by him when he was writing Opticks. The telescope appeared some time later in the shop of Heath and Wing instrument makers along with an instrument of Newtons belonging to Edmond Halley. It is most likely that the telescope had passed to Halley and then to Heath and Wing. This third telescope had the mirror damaged in 1694 by Newton while trying to clean it. It is thought that the mirror was later refigured by restorers accounting for its plugged eyepiece hole at an appropriate distance for a 6.25 inch focal length mirror and the new eyepiece position for the current mirror focal length of 8.5 inches. The current brass eyepiece is not original and was added later. This telescope was restored by Heath and Wing and presented to the Royal Society in 1766 as the telescope that Newton had made. At a later date a plaque was added to this telescope with the incorrect inscription claiming that it was his first telescope and made in 1671. This telescope probably includes the original mirrors, reground, part of the original base, the original support bar and possibly the original tube or parts of it.