This paper presents the analytical deduction of generic and unified equations of the movement of solar tracking systems. These equations reproduce published equations, which only consider the sun position, or the equations of the astronomical movement. As a novelty, these equations are more generic, thus allowing the optimization of the positioning of PV installations where diffuse and reflected irradiance are usable. The analysis of the results obtained criticizes the axiomatic idea - widely considered by numerous authors - establishing that the ideal tracking system in PV installations is that tracker providing the best possible alignment with direct sunbeams. (C) 2017 Elsevier Ltd. All rights reserved.