Gallucci, a Venetian scholar, was interested in astronomical instruments, both physical and on paper. The “Theater of the World” features a parade of rotating wheels, or “volvelles,” descendants of the astrolabe. These were paper instruments used to predict the positions of the Sun, Moon, planets and stars.
Gallucci’s star positions, with constellation figures, appear in Book V. Rulers along the borders established a grid for plotting star positions accurately. Gallucci’s book was the first star atlas to do so in both celestial latitude and longitude. The trapezoidal shape of the grid better accommodates the curved surface of a sphere. Gallucci took his star positions from the star catalog of Copernicus. The constellations are the 48 ancient constellations listed by Ptolemy; today, 88 constellations are officially recognized.