September marks the 300th anniversary of the death of Giovanni (Jean) Cassini, the Italian astronomer. Cassini discovered four of Saturn’s moons and was a co-discoverer of Jupiter’s Great Red Spot. He spent the first 20 years of his career at an observatory outside Bologna, Italy, and later became the director of the main astronomical institute in France, the Paris Observatory. NASA named the Saturn probe which launched in 1997 “Cassini” in his honor.
Special Collections owns several astronomical treatises written by Cassini, including this book, Observations sur la comete, detailing Cassini’s observations of a comet which appeared December 1680-March 1681 (click on the smaller image to the left to see Cassini’s observations of where the comet appeared on consecutive nights in February and March). This book and other early works on astronomy are part of the library’s History of Science Collection. You can find them in the library catalog by searching with the subject term, “Astronomy early works to 1800.”