Zanotti observes the Great Comets of 1744 & 1769

COMETS. Zanotti, Eustachio (1709-1782)

Osservazioni sopra la Cometa dell’ anno MDCCXLIV fatte nella Specula dell’ Istituto delle Scienze di Bologna nè mesi di Gennajo, Febbrajo, e Marzo da Eustachio Zanotti, ... e da Petronio Mateucci.

Bologna: Stamperia di Lelio dalla Volpe, 1744


Quarto: 24 x 17.5 cm. 16 pp. with one folding engraved plate (bound with:) 

Eustachio Zanotti. De cometa anni 1769. Sermo habitus in Academia Bononiensis Scientiarum Instituti die XXIII. Novembre ab Eustachio Zanotto ... 

Bologna, Typis Laelii a Vulpe, 1770 

Quarto: 8 pp. 24 x 17.5 cm.

FIRST EDITIONS. Disbound and stab-stitched. Both works in fine condition with broad margins. The plate is in equally fine shape. Very rare. Three copies of the first work located in North America (Yale, NY Public, Adler Planetarium) and no copies of the second.

Two rare works by the versatile observer and director of Bologna observatory, Eustachio Zanotti (1709-1782), regarding the great comets of 1744 and 1769, and with an engraved plate of the 1744 comet.

The Great Comet of 1744 (C/1743 X1), also called Comet Klinkenberg-Chéseaux, was discovered in November 1743 and was so bright that it became visible to the naked eye for several months in 1744. It was first observed on 6 January between the constellations of Pegasus and Andromeda. It achieved an estimated magnitude of -7 in February. The engraved plate shows the path of the comet, as observed from Bologna, from January 8th to March 4th, passing from Andromeda, through Pegasus, and into Aquarius. Zanotti records that this comet was the largest and brightest of those that he had observed in recent years (1737, 1739, 1742, 1743), which made it possible to observe its passage by day along its meridian and even when at conjunction with the Sun.

The Great Comet of 1769 (C/1769 P1) was discovered by Charles Messier on 8 August. On August 28th, Zanotti noted a tail length of about 15 degrees (while on August 30th, Captain James Cook, on board the Endeavor in the South pacific, measured the tail at 42 degrees.) Zanotti tells us that he was aided in his observations by Petronio Matteucci (b. 1717), his longtime assistant and collaborator. This would be the last comet observed by Zanotti.

Eustachio Zanotti belonged to a prominent family distinguished in the arts, letters, and sciences. He was educated by the Jesuits and entered the University of Bologna, becoming Eustachio Manfredi’s assistant at the Istituto delle Scienze in 1729. He obtained his first university post in 1738, after presenting his trial lecture on the Newtonian theory of light. In 1739, Zanotti succeeded Manfredi (who died in February) as director of the Institute observatory. 

Zanotti had established a reputation as an astronomer even before Manfredi’s death, through the discovery of two comets, to the second of which (1739) he attributed a parabolic orbit. When Zanotti was appointed director of the Institute, he had at his disposal state-of-the-art instruments, ordered by Manfredi in London and delivered in 1741: a mural quadrant with a radius of 1.2 m., a transit instrument with a focal length of 1 m., a movable quadrant, and a small reflecting telescope built by Jonathan Sisson. With the acquisition of these instruments, Zanotti’s observatory became one of the finest in Europe.

Zanotti’s principal observations and descriptions, including some on occultations of stars by the moon, concern six comets (1737, 1739, 1742, 1743-1744, Halley’s comet of 1758, and 1769), four lunar eclipses (December 1739, January 1740, November 1745, June 1750), three solar eclipses (August 1738, July 1748, January 1750), the aurora borealis (December 1737, March 1739), and transits of Mercury (1743, 1753) and of Venus (1751) on the sun.

Zanotti worked with his assistants Giovanni Angelo Brunelli, who would later become mathematician to the king of Portugal, and Petronio Matteucci, conducting countless observations of the sun, moon, planets, and comets, and compiling a catalog of 446 stars, mostly in the zodiac.

I. Riccardi, Bib Matematica Italiana, Pt. I, vol. 2, col. 652, no. 9; II. col. 656, no. 38