Newton's telescope, an examination of the reflecting telescope attributed to Sir Isaac Newton in the possession of the Royal Society

Abstract

Isaac Newton (1642-1727, F.R.S. 1672, P.R.S. 1703-1727) is generally I credited with the invention of the reflecting telescope, having conceived the idea in 1666* (1, 2, 3). In fact Gregory (4) and others (5) had by that time already considered telescopes employing curved mirrors, but late in 1668 Newton was the first to construct a working model (1,6). This instrument was also the first to employ a small elliptical plane mirror, inclined at 450 to the optic axis, to reflect the convergent beam from the primary mirror to an eyepiece mounted on the side of the telescope tube—a compact and very successful design now universally recognized as the Newtonian reflector. A second instrument made in the Autumn of 1671 (2) proved ‘sensibly better’ than the first. W ord of the invention reached the Royal Society, and Newton was invited to send a telescope for inspection by the Fellows. He dispatched the recentlycompleted second model, and it arrived in London in December 1671 (6, 7). At the meeting held n January 1672 (8) it was announced that the telescope had been examined at Whitehall by the King (Charles II), the President (Lord Brouncker), Sir Robert Moray, Sir Paul Neile, Dr Christopher W ren, and Mr Hooke; and they had formed so good an opinion of it that they had requested the Secretary (Henry Oldenburg) to send a formal description of the instrument to Christiaan Huygens in Paris, in order to secure the rights of the invention to Newton.