It is cited in the Instrumentum donationis of 1712 as: "Telescopium optimae notae, perspicillis duobus convexis, tubo e bractea ferrea, pedum Bonon. X & semis, a Campano elaboratum. Est illi Tubus alter chartaceus productilis, vagina coriacea custoditus. In hoc tria ocularia perspicilla, loculamentis suis inserta, asservantur, quae eidem Telescopii objectivo conveniunt, & terrestribus Corporibus inspiciendis inserviunt."
The tin tube, the three eye-piece lenses and the object lens mounting are all missing, with only a threaded wooden ring remaining on the extendible tube designed for the mounting of the object lens itself. A later mounting is also missing consisting of a square wooden tube [file 31].
The surviving object lens is in slightly yellowish green-tinted glass, with few bubbles, diameter 7.5 cm, ground edge 0.4 cm thick, focus 410 cm, equal to 10.7 Bolognese feet. It is signed Giuseppe Campani in Roma.
The cardboard tube (without lens) of a 3-lens erecting eye-piece, called Campanina (see Daumas, op.cit.) from the name of the craftsman, is still with us. This type of erecting optical system, though made up of lenses of the same glass, for the particular choice of their focal lengths, worked without affecting the chromatism of the image formed directly by the object lens. Part of Campani’s fame was due to the invention of this optics system: Huygens’ eye-piece, comprising two flat-convex converging lenses, was associated with the system of image inversion created by Campani, consisting of two converging lenses of equal focal length.
The six-draw tube is long, closed 134 cm, has an external diameter of 9.5 cm and is covered in gold-decorated black skin. The inner tubes are made up of a thin layer of wood, covered on the outside by paper stamped with blue geometrical shapes and on the inside by recycled writing paper. Once opened to the markings indicating correct extension for focusing purposes, it can be adjusted from 435 cm to 474 cm, including the eye-piece tube. This latter is 41.7 cm long and the ring to put the eye to is missing. Its diameter is 4.8 cm and is made up of four parts screwed together so as to allow three lenses to be inserted of diameters 3.9, 4.3 and 3.8 cm respectively, placed 11.7, 23.5 and 40.3 cm from the eye.
The telescope was used from 1702 with the tin tube, as witness a letter Manfredi sent general Marsili on 4 July of that year. It is also mentioned in a previous letter of Manfredi to Marsili of 10 January 1702 as one of the instruments given Manfredi by the general’s brother, Count Filippo. The extendible tube looks very worn and so the telescope must date from a much earlier period, even if Ceschi, in the 1843 inventory, indicates a date of 1700 for the object lens.
The Schedae Mathematicae of Vittorio Francesco Stancari (Bologna 1713, p. 87) records that the telescope was used for the first time by Manfredi and Stancari on January 4, 1702.
It was restored in 1993 by N. Scianna (Forlì).
E. Baiada, A. Braccesi (1983), p. 84.
M. Daumas (1953), p. 88.
M.L. Righini Bonelli (1981).