ABSTRACT
The name spherical astronomy indicates the systematic and formal representation of the positions and angular movements (motions) projected on the celestial sphere of the heavenly bodies. The name astrometry indicates the several methods of measurement and data reduction. When the distances of these bodies are known, their position in the Cartesian space, velocities and accelerations can be determined. In this chapter, the authors begin the study of spherical astronomy, using essentially geometric concepts, without considering the physical bases of the phenomena. Historically, this is the way astronomy began several millennia ago, leading to the geocentric conception of the world that found its maximum expression in the Ptolemaic theory. The authors provide notions of plane and spherical trigonometry needed in the rest of this book.
