CLAVIUS, Christoph (1538-1612). In Sphaeram Ioannis de Sacro Bosco Commentarius. Rome: Victor Helianus, 1570.

Crisp first edition of Clavius's commentary on Sacrobosco's classic astronomical text, with extensive manuscript additions and corrections probably done in the printer's shop. Clavius’s detailed commentary sought to bring the Ptolemaic astronomy of Sacrobosco up-to-date with sixteenth-century astronomy, and it quickly became a standard textbook in its own right. Despite being a friend of Galileo, Clavius's "update" to astronomy stopped short of Heliocentrism. Indeed, in a later edition of this commentary he condemned Copernicanism as absurd—although he otherwise respected the father of Heliocentrism, and even defended Galileo after the publication of Siderius nuncius. This copy has extensive manuscript annotations, additions, and corrections to the text on a total of 32 pages. These additions are incorporated in subsequent editions of Clavius’s commentary (1581 and later). There are other copies of the 1570 edition with the same additions, done in the same hand. These were obviously corrections carried out, probably in the printer’s shop, at the behest of Clavius. Sommervogel II 1212 1. Houzeau & Lancaster 2678.

Quarto (205 x 148mm). Woodcut armillary sphere on title, woodcut printer’s device on colophon leaf, and numerous woodcut illustrations in text (occasional toning and spotting, heavier at end; a slim dampstain at outer edge of early gatherings; gathering C sprung). Contemporary limp vellum, remains of ties.