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.