Astronomical Images : Armillary sphere with zodiac

Johannes Sacrobosco

Astronomical Images

<p style='text-align: justify;'>Very little is known about Johannes Sacrobosco except that he was probably British, taught astronomy at Paris University, and died there in the second quarter of the thirteenth century. <i>Sphaera mundi</i>, his major work, was an extraordinarily popular astronomical textbook for several generations. Manuscripts of it circulated through all the main European centres of learning. It was first published in 1472 in Ferrara, and went through dozens of editions up to the mid-seventeenth century. This is from one of the first Italian translations of Sacrobosco's <i>Sphaera</i>, to which Fra Mauro Fiorentino added a short treatise on cosmography, navigation, altimetry and stereometry. Fra Mauro Mattei from Florence or Fiorentino (c. 1493-1556) was a Servite active at the Annunziata Church in Florence. His interests covered several mathematical disciplines, including music (on which a treatise by him survives at the Laurenziana Library). At the beginning of his edition, Fra Mauro included a dedicatory letter to Giovan'Orthega de Carion, from the Annunziata Church, 1537. This Italian translation of Sacrobosco's classic work on the Sphere would have provided a useful resource for those who wanted to improve their knowledge of cosmography but lacked the Latin skills to read the original text, or preferred to read the vernacular version. This figure shows an armillary sphere, which the caption describes as a 'Figure of the accidental sphere imagined, that is, mathematical'. The adjective 'accidental' refers to Sacrobosco's classification of the sphere into substantial and accidental parts: 'By accident the sphere is divided into the sphere right and the sphere oblique. For those are said to have the sphere right who dwell at the equator, if anyone can live there. And it is called 'right' because neither pole is elevated more for them than the other, or because their horizon intersects the equinoctial circle and is intersected by it at spherical right angles'.</p>