A Venetian astronomer, mathematician, and scientific-instrument maker, Facini was also the author of various inventions: the surveying protractor with magnetic compass (1694), now in the Naval History Museum of Venice; the proportional cyclometer, for calculating curved areas, described in his treatise on the Anatomy of the circle in its quadrature (Cologne, 1695); the nautical compendium - now in the Hermitage of Saint Petersburg - a compound horary instrument with a magnetic compass and a lunar-phase indicator to determine latitude, longitude, and the time during navigation; the trigrometron, for calculating the sides of triangles without knowing the angles; and the horometrum, to indicate the times of sunrise and sunset and the length of every day of the year. He also made magnetic compasses for the plane table, astronomical quadrants, graphometers, and - for the Margrave Wilhelm Frederich of Brandenburg-Ansbach - a measuring instrument for military use. In 1714, he built a logarithmic calculator (an example is preserved at the Adler Planetarium in Chicago). In 1717, he entered the service of the Duke of Parma, Francesco Farnese, for whom he restored a spherical mechanical clock (sferilogio) made by Bartolomeo Ferrari for Giovanni Gonzaga. In 1725, he completed an extraordinarily complex planetarium, which he called planisferologio, now preserved in the Vatican Museums.