31. Instrument for the object lenses of G. Campani by E. Lelli
Bologna, 1752
Ercole Lelli (Bologna 1702-1766)
red-fir wood
length from 720 to 980 cm

The Bolognese Prospero Lambertini, who became Pope Benedict XIV, bought, in 1747, the whole of Giuseppe Campaniís Rome workshop from his children, who had continued the work there, and donated it to the Institute of Science. A large number of relics by Campani, including hundreds of metal moulds for all the different work phases of the various types of lenses and a dozen or so extraordinary lenses of different focal length signed by the author, can today be seen at the Physics Museum of the University of Bologna.
In occasion of the donation, Ercole Lelli built an instrument for mounting Campaniís long focal object lenses which was set up in the then courtyard to the south of the tower.
In the Commentaries of the Institute of Science (Tomo III, 1755, p. 19) there is the following quotation marking the Popeís gift and describing Lelliís instrument:

"... Benedictus XIV ad omnes, quaecumque se darent, occasiones intentus, hanc arripuit: elaboratissima vitra, et lentes Campanae pulcherrimas,...,in Institutum invehi jusserat, & dioptricae officinam costituerat. Hic illum non fugit de Specula; duasque ex objectivis Campanae lentibus longe pulcherrimas, & foci distantia insignes, ad eam deferri jussit, quibus astronomi in subtilioribus capessendis observationibus, uti opus esset, uterentur. Egregium sane munus; nam lentes tales numquam antea bononiensis Specula obtinuerat. Quo etiam machinam condidit commodissimam, expeditissimamque, qua telescopia quaeque vel longissima possint dirigi. Longiora tamen quam quae memoratis modo lentibus componuntur, locus non capit. Haec adhuc ad Astronomiam accesserunt."
Lelliís instrument is not specifically mentioned in the inventories, but a hand-written note by Eustachio Zanotti in the 1746 inventory (reviewed after 1757) mentions the wooden tubes for Campaniís 11-foot lens, a 22-foot one and an unspecified 30-foot lens, similar in length to the 33-foot lens by Campani that is still with us.
Identically made wooden square tubes matching the above-mentioned specifications, and a few relative accessories, have been traced and are listed as follows: The first three tubes are reinforced by lagging at the eye-piece end to withstand introduction of the tubes. Into the last tube at the eye-piece end fits a pasteboard tube [Inv. MdS-191] with a 55 mm-diameter threaded ferrule for attaching two eye-pieces (lenses missing today), one with a focus of about 10 cm [Inv. MdS-192], the other [Inv. MdS-36], with the section bearing the field diaphragm missing, about 12 cm. Maximum magnification at maximum length would have been 196 times and, with the 33-foot object lens, 129.
None of the mounts of the bigger lenses have been found. The eye-piece tube has survived, comprising three colored cardboard tubes with black wooden ferrules 41, 42 and 30.5 cm long respectively and diameters of 5.5, 6 and 7 cm [Inv. MdS-133a,b,c].
Lelliís instrument most likely resembled the one illustrated in table VIII of Francesco Bianchiniís Hesperi et Phosphori nova Phaenomena sive observationes circa planetam Veneris, published in Rome in 1728, which was also made up of square tubes. Some pulleys and a counterweight have in fact been found which could have belonged to an instrument of that kind.

The instrumentís mount - using the tubes designed for Campaniís 22-foot object lens [file 29] - was restored in 1985, building a new stand and a leaf-spring to stop the telescope bending. The sighting and pantograph guide system was also rebuilt on a support stand of the period [Inv. MdS-61], using Christiaan Huygensí description of a similar instrument (table XXXI of first volume of Opera Varia published by J. Vander in 1724).

E. Baiada, A. Braccesi (1983), p. 120.
F. Bianchini (1728), tav. VIII.
M.L. Righini Bonelli (1981).