Journal of Astronomical History and Heritage, 20(2), 271‒288 (2017). FRANCESCO FONTANA AND THE BIRTH OF THE ASTRONOMICAL TELESCOPE Paolo Molaro INAF, Osservatorio Astronomico di Trieste, Via G.B. Tiepolo 11, 34143 Trieste, Italy. E-mail:
[email protected] Abstract: In the late 1620s the Neapolitan Francesco Fontana was the first to observe the sky using a telescope with two convex lenses, which he had manufactured himself. Fontana succeeded in drawing the most accurate maps of the Moon’s surface of his time, which were to become popular through a number of publications that appeared throughout Europe but did not acknowledge the author. At the end of 1645, in a state of declining health and pressed by the need to defend his authorship, Fontana carried out an intense observing campaign, the results of which he hurriedly collected in his Novae Coelestium Terrestriumque rerum Observationis (1646), the only public- cation he left for posterity. Fontana observed the Moon’s main craters, such as Tycho (which he referred to as ‘Fons Major’), their radial debris patterns and changes in their appearance due to the Moon’s motion. He observed the gibbosity of Mars at quadrature and, together with the Jesuit Giovanni Battista Zupus, he described the phases of Mercury. Fontana observed the two—and occasionally three—major bands of Jupiter, and inferred the rotation of the major planets Mars, Jupiter and Saturn, arguing that they could not be attached to an Aristotelian sky. He came close to revealing the ring structure of Saturn. He also suggested the presence of additional moons around Jupiter, Venus and Saturn, which prompted a debate that lasted more than a hundred years.