ABSTRACT
The name spherical astronomy indicates the systematic and formal representation of the apparent positions and motions of the heavenly bodies such as they appear projected on the celestial sphere. This chapter begins the study of spherical astronomy, using essentially only geometric concepts, and without considering the physical bases of the phenomena. The name spherical astronomy indicates the systematic and formal representation of the apparent positions and motions of the heavenly bodies such as they appear projected on the celestial sphere. Dynamical astronomy studies those positions and motions in the Cartesian space, and investigates the responsible forces; the name celestial mechanics is also used for this discipline. Spherical trigonometry finds its origins in the Greek world, with Hipparchus of Nicea, and then with Claudius Ptolomeus. The direction of the longitude can also vary according to the application, sometimes it increases in the conventional way of trigonometry, in other instances the opposite verse is adopted.
