SACROBOSCO, Johannes de. [with] REGIOMONTANUS, Johannes. [and] PURBACH, Georg.

Very good, well-margined and handsomely illustrated copy of the first edition of this important collection on Ptolemaic astronomy intended for students, and the most widely used of the early modern period. Johannes de Sacrobosco (or Holywood, 1195-1256) was a monk and astronomer who taught at Paris. His ground-breaking works were extremely influential in the medieval period; they focused on astronomy and mathematics including the Hindu-Arabic numeral system, a study of the shortcomings of the Julian calendar (anticipating C16 debates) and his treatise ‘Sphaera mundi’. First published in 1472, it was reprinted dozens of times in Europe throughout the C15. It discusses the earth in relation to the geocentric Ptolemaic universe, touching on subjects including its physical composition, geometrical realization, its (as it were) sphericity, the revolution of the heavens and the zodiac in relation to sunrise and sunset, the meaning of zenith and climate zones. Johannes Regiomontanus (Müller von Königsberg, 1436-76) studied at Leipzig and Vienna, devoting himself to commentaries on ancient texts on arithmetic and astronomy. He established the first astronomical observatory in Nuremberg. His work argues against the ‘deliramenta’ of Gherardus Cremonensis’s Ptolemaic ‘Theorica Planetarum’, written in the C12 and the most important manual of astronomy used in Faculties of Arts. Structured as a dialogue between two scholars, it concerns calculations relating to very specific points of the Ptolemaic system, e.g., epicycles and longitude, with the help of geometrical diagrams. The last work—‘Theoricae novae planetarum’—was written by Georgius Purbach (von Peuerbach, 1423-61), an Austrian astronomer and mathematician, acquainted with Regiomontanus. It is a clear introduction to the Ptolemaic universe which discusses the sun and moon, theories of the polar axis and astronomical connections between the moon and the motions of other planets. The early C16 annotator of ‘Sphaera mundi’ was probably one of the ‘novicii adolescentes’ (young students) to whom the works were addressed. He applied sundry learning techniques, which shed light on the teaching of astronomy: the typically medieval and early modern interlinear paraphrasis (the rewriting of a concept using synonyms, e.g., ‘ascensu’ for ‘ortu’); marginal glosses (e.g., the astronomical concept of ‘annus bisextilis’, a clarification of the meaning of ‘opposition’ for the zodiac); and the clarification of sources (e.g., the specific book in which Euclid discusses the geometrical ‘sphaera’). A most interesting copy.