A Vallombrosan monk, Guidi was a student of optics, botany, philosophy, and literature. He taught philosophy in the monastery of Passignano (Florence), where he also introduced mathematical disciplines. He set up an optical workshop, in which he made many scientific instruments, such as reflecting and Galilean telescopes, solar microscopes, and camera lucidas. In 1772 he became perpetual abbot of the Badia di San Bartolomeo in Pistoia, where he left a small but well-equipped astronomical observatory, in which he received Grand Duke Peter Leopold (1747-1792) on several occasions.