The Recensio suppellectilis astronomicae... of 1727 records this telescope of over five metre focal length, donated by Cardinal Davia: "Ex munere Emi. Card. De Via/Telescopium pedum 14 circiter perspicillis convexis, cuius tubo e’ bractea ferrea."
In 1746, on the other hand, separate mention is made of "a fourteen-foot tin tube for an object lens by Celio" and "a fourteen-foot object lens by Celio in a wooden box". Both can be identified with the telescope cited in 1727, even if the usual mention of the donor is missing. The tin tube has not been found but the object lens remains, made of white glass with bubbles - focal length 540 cm, or 14.1 feet, diameter 8.7 cm and edge thickness 3.1 mm - with engraved the words Marcus Antonius Cellius f. Romae Anno Dom. 1685.
There is little known about this optics expert even though he did observe the satellites of Jupiter and comets for G.D. Cassini. We still have his book Descrizione d’un modo di trasportare qualsiasi figura disegnata in carta..., printed in Rome in 1686 for the Komarek printing house.
E. Baiada, A. Braccesi (1983), p. 88.
G. Horn-d'Arturo, P. Tempesti (1960), p. 235.