Eustachio Divini (4 October 1610 – 22 February 1685) was an Italian manufacturer and experimenter of optical instruments for scientific use in Rome.
The origins Eustachio was born on 4 October 1610 in San Severino Marche, from the illustrious Divini's family. At the age of four his mother, Virginia Saracini, died and seven years later his father, Tardozzo Divini, also died, so his brothers Vincenzo and Cipriano looked after him and his basic education before moving to Rome. At that time Divini was initiated into the military career but after a severe disease in 1629 he had to give up. After that he joined again his brothers.The content of this article is partially translated and adapted from the essay of Gualberto Piangatelli Biography of Eustachio Divini with the contribute of students and teachers of ITIS "E. Divini" in San Severino Marche, Italy.
The Roman career His brother Vincenzo, who frequented the literary and scientific circle in Rome, incited him to follow the lessons of monk Benedetto Castelli, disciple of Galilei. So Eustachio began his new fertile formative experience with people of his same generation such as Evangelista Torricelli, Giovanni Alfonso Borelli, Bonaventura Cavalieri and Michelangelo Ricci. In the early 1640s Divini practiced as a clock-maker. Subsequently, his good relationship and friendship with Torricelli led him to cultivate a shared interest, the construction of optical instruments, microscopes and telescopes and their improvement. Divini's factory of instruments was located in the area of Navona square in Rome, and it is very probable that quite a high number of artisans (mechanics, glassmakers, tanners etc.) where working under Divini's direction.Roberto Buonanno: Il Cielo sopra Roma: I Luoghi dell'astronomia Ed. Springer pag. 17 Since 1646 to about mid-century his lenses and glasses spread all over Europe granting him the role of Italy's foremost optician.
Many types of telescopes of various lengths were owned by prominent secular and ecclesiastic authorities in Rome. Divini's reputation and earnings were obtained not only thanks to the manufacture of optical instruments, but also thanks to the frequenting of a circle of scholars of the Roman College, where the astronomical research and the quality of the instruments of observation were both important. Differently from Francini, Galilei's artisan, this group produced new working methods and new optical systems. These discoveries were published and spread all over Europe. The Court of Medici in Florence bought many Divini's telescopes and was not only a test bench for him, but also a spreading engine for the notoriety of the optician, because of the role of the associated Accademia del Cimento in triggering astronomical research in all Europe. So it isn't a surprise that the prestigious Royal Society of London dedicated to Divini with the inscription: "Divinus Eustachius: De Sancto Severini, Insignis Mathematicus". The astronomers of the Accademia del Cimento substituted several Divini's objectives for Torricelli's lenses, obtaining a perfect combination with Divini's convex oculars and composed eyepieces. Recent tests and analysis of telescopes conserved in Florence Science Museum confirm these changes on Divini's telescopes and the better quality of Torricelli's objective lenses.Albert Van Helden, Catalogue of early telescopes, Istituto e museo di storia della scienza (Italy), 1999. (preview)
Divini's first publication was a print appeared in 1649 where he intended to document the possibilities offered by his telescopes. Indeed, at the centre he depicted a selenographyenlarged image of Divini's most famous achievement derived from his observations of the full moon in March 1649, using two telescopes, and around the crescent Saturn, Venus and Jupiter. He deserved fame mainly for his use of micrometer eyepiece consisting in a grid of wires inserted in a biconvex eyepiece, thanks to which he could draw the moonspots in the exact position. A copy of that selenography was given later by Eustachio Divini to his hometown San Severino, his birth town he kept in touch continuously together with his brother Cipriano, a well-established painter in Rome.
Divini's contributes to microscope optics and mechanics, shared with Campani brothers (Giuseppe and Matteo), are unquestionable.history of microscope technology, by Institute and Museum of History of Science, Florence He designed, among the others, coupled lenses to reduce chromatic aberration,Description of a new Microscope Divini's paper on Philosophical Transactions of Royal Society, 1668Divini's contribution to limiting chromatic aberration devised a mirror to send light onto the specimen to be observed,Erich HINTZSCHE, L'invenzione del microscopio, in "Rivista Ciba", n. 27, December 1950, Milan, pp. 870–871 and created the Vase microscope.Divini's Vase microscope quoted for having been used by Malpighi in his discovery of red blood cells flowing in capillaries around 1660.
Eustachio Divini re-discovered the spot, the satellites shadows and the changing shape belt upon Jupiter in 1665,"lettera di Eustachio Diuini intorno alle macchie nuouamente scoperte nel mese di luglio 1665 nel pianeta di Gioue con suoi cannocchiali, all'illustrissimo a Carlo Antonio Manzini 1666", free search in IMSS Florence with his telescopes (after the astronomer Giovanni Domenico Cassini who first used Divini's telescopes when he was living in Rome). These discoveries had permitted previously to argue out the rotation of Jupiter around its axis, whereas Divini was able to demonstrate the amateurs and astronomers community that his instruments were as effective as the ones made by his rivals, Campani brothers, manufacturer of telescopes for Cassini.
Challenges and disputes It was around the middle of seventeenth century, after the development of telescope handicraft initiated by Galilei, Francini, Fontana, Torricelli and others; that direct comparisons of telescopes – paragoniCourt Scientists, Institute and Museum of the History of Science, Florence Go to: The Comparison of Telescopes – became regular and exciting events in the Italian world of science, also hailed by the Accademia del Cimento in Florence, one of the earliest societies dedicated to the experimental method. Eustachio Divini was one of the protagonists, against his will, of these contests.
Divini's reputation as the best European maker of telescopes begun to be superseded in 1656, when Christiaan Huygens announced the discovery of a "moon" of Saturn (the satellite that was called Titan later on). The Dutch astronomer, discovered it in 1655 using his own telescopes, then followed its movements for months, seeing the satellite make a complete revolution of Saturn "arms" every sixteen days. During those months he recognized also phases of different width in the anses, the mysterious formation accompanying the planet, and reasoned that If that body had to rotate remaining attached to the planet in a few days, its appearance should have been changing shape more frequently than it did. He recognized the role of that fortuitous circumstance in permitting him to guess and declare – in 1659 – the real nature of the planet's ring. Nevertheless, while writing: "I perceive this ring very plainly with the eyes", he was underestimating the role of his insights and gestalt switch for the interpretation of what he had seen. We can interpret Huygens' worry to attribute his discovery to a visual fact as a sort of pre-defensive attitude, demonstrating that any change of the heavens based on the strongest logical reason, was still hampered by the Inquisition in that post-Galilean age.
So Huygens, in his memorial dedicated to Prince Leopold of Medici,Huygens' Systema Saturnium, 1659 suggested that the previous wrong interpretations as "opposite bodies" or "handle like formations" of Saturn ring were due to the inferior quality of the instruments. In the same opera Huygens attributed to Divini's silkscreen the most faithful representation of the planet in circulation, while congratulating him as "praestantissimus percillorum artifex", but he ascribed to Divini's – and criticized as intentional – the introduction of "arbitrary nonexistent shadows, darker than the sky, between the body of the planet and the "bent handles". Divini, who just wanted to represent the best that his telescopes permitted to see and not to solve astronomical queries, resented Huygens' criticism. Also Divini had noticed in 1657Fabri Honoré; Eustachii de Diuinis Brevis annotatio in systema Saturnium Christiani Hugenii, 1660 download Latin original text searching for Divini in IMSS Florence the satellite of Saturn, which previously he had considered a simple fixed star. Actually, the gap of the quality of his observations wasn't big (all the instruments of that age had a resolution not better than 10'’, as to say that Saturn's ring was indeed invisible to everybody.Analysing Early Observations, IMSS Florence But perhaps, as it often happens in Science, it was the availability or the insight of a good theory to allow Huygens a better representation of the whole Saturn's system. Unfortunately Huygens's attitude offended Divini and provoked a series of attacks and retorts that led to mutual insults.
As Divini was unable to write in Latin, he asked Honoré Fabri (a powerful French Jesuit anti-Copernican who lived in Rome and was user-estimator of Divini's telescopes) to translate his defense of the effectiveness of his own telescopes. But Fabri imposed on Divini by making an issue out of Huygens' avowed Copernicanism, imagining a number of light and dark satellites moving behind the planet in tight formation, in such a way to reproduce the appearance of the anses. The academicians of Cimento in Florence were involved in the quarrel receiving the Brevis annotatio in Systema SaturniumInOpera Astronomica pag. 597 signed only by Divini. Huygens promptly replied as soon as he became aware – thanks to Pierre Guisony that was living in Rome in contact with Fabri – that Divini was preparing an offensive.Christiaan Huygens, Oeuvres Complètes, Vol. III. Correspondence, n. 769, August, 13th 1660, from Huygens to Leopoldo de Medicis pag. 127Christiaan Huygens, Oeuvres Complètes, Vol. III. Correspondence, n. 783, September, 30th 1660, from Huygens to Leopoldo de Medicis pag. 152
Prince Leopold, a skilled astronomer, knew that the question of telescopes was disjointed from the theoretical one, and he was yet perfectly acquainted with Divini's telescopes quality. In fact in 1660 he had viewed Saturn's shadow on its ring with a telescope made by Divini,Albert Van Helden, Saturn and his Anses, in Journal for the History of Astronomy, V, 1974, pag. 130, pag. 151 a result that Huygens would have been looking for a long time yet. So he proposed Huygens to submit his better telescope to a test in Holland, while the same test would be done in Italy to Divini's better telescope.Christiaan Huygens, Oeuvres Complètes, Vol. III. Correspondence, n. 730, March, 16th 1660, from Carlo Dati to Nicolas Heinsius pag.63
Huygens did not comply, but, in September 1660, after receiving a full copy of Divini's booklet Brevis Annotatio, published a complete reply,Brevis Assertio Systematis Saturnii, once again addressed to the Prince LeopoldChristiani Hugenii; Breuis assertio systematis Saturnii sui ad serenissimvm principem Leopoldum ab Hetruria, Latin, 1660 pag. 619 diminishing both his opponents, and humiliating Divini with the name of "vitrarius artifex" (glassworker).Christiani Hugenii; Breuis assertio systematis Saturnii sui ad serenissimvm principem Leopoldum ab Hetruria, Latin, 1660 pag. 627