Gregorian reflecting telescope, said to have made by John Hadley in 1726, although stylistic features would suggest a later date of c.1740. The telescope has a 2-inch metal speculum mirror with a focal length of 14 inches and a sharkskin covered brass tube with metal case.
Dated 1724, this telescope has been described as the earliest example of a reflecting telescope using the Gregorian optical configuration. The Scottish mathematician, James Gregory first suggested this optical layout in 1663. Yet he was unable to have it made due the difficulty of making mirrors with non-spherical surfaces. Over fifty years later, Hadley succeeded where Gregory failed, after making a reflecting telescope using Isaac Newton's principles in 1721. He presented his Newtonian Telescope to the Royal Society of London who found it performed favourable with the best of telescopes then available. Although having remained in the Hadley family until the nineteenth century, it seems likely, from style and design, that this Gregorian telescope was made later around 1740.