The Merz 12.8-inch Telescope was ordered in 1855 and brought into use in 1860. It was the Observatory's largest equatorially mounted refractor until the arrival of the 13-inch Astrographic Telescope in 1890. Both the telescope and its mounting were designed by George Airy and were referred to together as either the Great Equatorial or the South-East Equatorial. The telescope had an object glass of 12.8-inches diameter and a focal length of 17 feet 10 inches. This series is comprised of a large set of drawings of George Airy's New Equatorial Refractor. Many are heavily annotated with notes by Airy. They are arranged in two sets by size (the first set /1-94 being larger) and, within each set, by drawing number. At the end of the series is a drawing of the Great Equatorial dome, and various unnumbered drawings including one by Howard Grubb dated 1887, titled, 'Rough design for photographic equatorial'. Also included is a 1970s copy drawing (at RGO 101/2/11/6). Note: classmark /38 not assigned.