Reference Work Entry

Biographical Encyclopedia of Astronomers

pp 357-358

Date:

Campani, Giuseppe

Born Castel San Felice, (Umbria, Italy), 1635

Died Rome, (Italy), 28 July 1715

Giuseppe Campani was one of Europe’s foremost telescope makers and opticians in the seventeenth century. Born in a village near Spoleto, he came from a peasant family and had no university education. He soon went to Rome with his two brothers, one of whom was a cleric, the other a clockmaker. Campani learned clockmaking, probably studied optics at the Collegio Romano, and became skilful in grinding lenses.

In 1656 Campani, along with his brothers, made a silent night clock, which, when presented to Pope Alexander VII, brought him fame. He then became a full-time lens grinder, a trade carried out for nearly 50 years, constructing telescopes and lenses in Rome. He worked for important individuals all over Europe and for the Royal Observatory in Paris. The Pope and his nephew, Cardinal Flavio Chigi, remained among Campani’s most important patrons, but he also won the patronage of Ferdinand II, Grand Duke of Tuscany, and of Cardinal Antonio Barberini, who took the first Campani telescope out of Italy to Paris, where he exhibited it.

In 1664 Campani developed a lens-grinding machine; there is a controversy over whether it could polish lenses without the use of molds. (A number of Campani’s molds do survive.) He was able to fashion the best composite eyepieces and lenses, primarily for telescopes but also for microscopes. He also improved telescope tubes by constructing them of wood rather than of cardboard covered with leather. Even if this design was somewhat unwieldy, it proved durable, and wooden telescopes continued in use until the nineteenth century.

Campani made some significant observations with his own instruments. Between 1664 and 1665, particularly, he observed the moons of Jupiter and the rings of Saturn. His astronomical observations and descriptions of his telescopes are detailed in these papers: Ragguaglio di due nuove osservazioni, una celeste in ordine alla stella di Saturno, e terrestre l'altra in ordine agl'instrumenti (Report on two new observations, the one heavenly about Saturn, the other earthly about instruments), published in Rome in 1664 and again in 1665 and Lettere di G.C. al sig. Giovanni Domenico Cassini intorno alle ombre delle stelle Medicee nel volto di Giove, ed altri nuovi fenomeni celesti scoperti co' suoi occhiali (G.C.’s letters to Mr. Giovanni Domenico Cassini about Medicean stars’ shadows on the face of Jupiter, and other new heavenly phenomena discovered with his own telescopes), published in Rome in 1666.

A bitter rivalry grew up between Campani and telescope maker Eustachio Divini , who also worked in Rome. From 1662 to 1665 this rivalry became a hot dispute, and many “comparisons” were made between the instruments of the two. The first public comparison took place at the end of October 1663 in the garden of Mattia de’ Medici, in the presence of some famous astronomers like Giovanni Cassini . The contest ended in a draw, since they acknowledged that Divini’s telescope had a bigger magnification but Campani’s had a better focusing. Many other comparisons were made in the following months, but they virtually ended in July 1665, when Campani’s 50-span-long telescope was unanimously judged as the best ever constructed.

Early on, Cassini became convinced that Campani’s telescopes were better than Divini’s. Because of Cassini, Campani’s instruments equipped the Royal Observatory in Paris and all of Cassini’s discoveries were made with Campani’s telescopes.

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