Kommentar zu einem der wichtigsten astronomischen Lehrbücher des 16. Jahrhunderts durch den Jesuitenpater Christoph Clavius (1527-1612), der in insgesamt 19 Auflagen bis in das 17. Jhdt erschien.

Buch von Christoph Clavius. Es ist ein Kommentar zu dem Büchlein von Johannes von Sacrobosco, das wir früher gekauft haben. Christoph Clavius war einer der bedeutendsten Mathematiker des 16. Jahrhunderts. Berühmt wurde er durch seine Reform des Kalenders. Der Gregorianische Kalender wurde von ihm berechnet.

Probably sixth edition of Clavius' commentary on the 'Sphere' of Sacrobosco, with extensive manuscript additions and corrections to the text which were incorporated in subsequent editions. Clavius's detailed commentary, which occupies the majority of the text, sought to bring the Ptolemaic astronomy of Sacrobosco up-to-date with later sixteenth-century astronomy, and it quickly became a standard textbook, going through several editions.

Clavius taught a course in astronomy at the Collegio Romano for which this commentary served as the textbook.Clavius (1537-1612), a Jesuit from Bamberg, was a friend of Galileo but never wavered in his geocentric beliefs. In fact, in the 1581 edition of this work, he condemned Copernicanism as physically absurd, although elsewhere he speaks with praise of Copernicus. When Galileo published the Siderius nuncius in 1610, Clavius was one of his principal defenders. He had a telescope constructed and was able to verify Galileo's observations of the satellites of Jupiter and the shape of Saturn.