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In contrast to the constellation figures in Hyginus and Abu Ma’shar, Piccolomini created a star atlas, measuring the positions of the stars according to an indicated scale (specific to each plate). He designated stars by Roman letters (a, b, c, etc.) in order of apparent brightness. Piccolomini also indicated brighter stars by showing them larger on the page.
Piccolomini, at the University of Padua at this time, published a number of works in the vernacular. His wrote an introduction to astronomy, The Sphere of the Universe (La Sfera del Mondo), in the Tuscan dialect. The 1st edition of La Sfera is included in this volume; 14 editions were published before the end of the century. Piccolomini was particularly interested in codifying the use of standard scientific terms in Italian, creating them when necessary, especially in astronomy.
Compare Piccolomini’s depiction of Orion with Galileo’s, who also declined to include a constellation figure.
Piccolomini’s plates are numbered according to Ptolemy’s list of 48 constellations, although the plate for Equuleus the Little Horse is missing from this and other known copies.
Constellation figures were not the only conceptual entities Piccolomini omitted: he was also skeptical of the reality of the geometrical devices used in astronomical systems, despite their effectiveness as calculation tools. For example, Ptolemy could model the motion of the Sun using either an epicycle or an eccentric model; these models could both provide accurate predictions of the Sun’s positions, but both could not be true. For Piccolomini, mathematical methods did not rise to the level of logical demonstrations.
Piccolomini was an advocate not only of science in the vernacular, but also of providing educational opportunities for women.