The long focus object lenses by Giuseppe Campani are never mentioned in the inventories. We know however, from the Records of the Specola (vol. IX, dated 26 October 1752, Archivio Dip. Astron. Bo.), that a 56-palm object lens, equal to 32.8 Bolognese feet, was tried out in 1752. This lens was found among those belonging to the Physics Museum and is now preserved in the Museo della Specola.
The object lens is in faintly green-tinted glass, with very few bubbles, has a diameter of 13.8 cm, a focal length of 1210 cm, a ground edge 0.5 cm thick, and bears the words Giuseppe Campani in Roma.
It was most probably used in one of the wooden tubes of the Macchina di Lelli [file 31], which is mentioned in the inventories as built for an undetermined object lens of thirty foot.
E. Baiada, A. Braccesi (1983), p. 120.
M.L. Righini Bonelli (1981).