Magini supported a geocentric system of the world, in preference to
Copernicus's heliocentric system. Magini devised his own planetary theory, in preference to other existing ones. The Maginian System consisted of eleven rotating spheres, which he described in his
Novæ cœlestium orbium theoricæ congruentes cum observationibus N. Copernici (
Venice, 1589). In his
De Planis Triangulis (1592), he described the use of
quadrants in
surveying and
astronomy. In 1592 Magini published
Tabula tetragonica, and in 1606 devised extremely accurate
trigonometric tables. He also worked on the geometry of the sphere and applications of trigonometry, for which he invented calculating devices. He also worked on the problem of
mirrors and published on the theory of concave spherical mirrors. He also published a commentary on
Ptolemy’s Geographia (Venice, 1596). As a cartographer, his life's work was the preparation of
Italia or the ''Atlante geografico d'Italia'' (Geographic Atlas of Italy), printed posthumously by Magini's son in 1620. This was intended to include maps of every Italian region with exact nomenclature and historical notes. A major project, its production (begun in 1594) proved expensive and Magini assumed various additional posts in order to fund it, including becoming tutor in mathematics to the sons of
Vincenzo I of Gonzaga,
Duke of Mantua, a major patron of the arts and sciences. He also served as court astrologer. The Duke of Mantua, to whom the atlas is dedicated, assisted him with this project and allowed for maps of the various states of Italy to be brought to Magini. The governments of
Messina and
Genoa also assisted Magini financially in this project. Magini did not do any of the mapping himself. A strong supporter of
astrology, he defended its use in medicine in his
De astrologica ratione (
Venice, 1607). Magini collaborated closely with
Valentine Naibod, and in this book he published
De annui temporis mensura in Directionibus and
De Directionibus from Naibod's unfinished manuscript
Claudii Ptolemaei Quadripartitae Constructionis Apotelesmata Commentarius novus et Eiusdem Conversio nova. He was also interested in
metoposcopy. He corresponded with
Tycho Brahe,
Clavius,
Abraham Ortelius, and
Johann Kepler. His correspondence was edited in 1886 by Antonio Favaro. Magini was an early critic of Galileo's 1610 identification of the Galilean moons of Jupiter and lunar mountains. Magini's one-time secretary,
Martin Horký, published an aggressively anti-Galilean pamphlet in 1610, though Magini cut ties with Horký shortly before it was published. The
lunar crater Maginus is named after him. A UK Software company takes their name from the Maginus crater named in his honour. ==Works==