Newton's telescope. Replica of the second reflecting telescope designed and built by English astronomer Sir Isaac Newton (1642-1727) in 1671. Newton invented the reflecting telescope in 1668 because he thought that it was impossible to produce a telescope lens that did not cause colour distortions (chromatic aberration). This telescope focuses light using a parabolic mirror, which is reflected back up the 30-centimetre long tube to another mirror. This second mirror reflects the image sideways through an eyepiece (upper right). This telescope was first demonstrated by Newton in 1672 at the Royal Society, London, England.