Abstract
Let a planet perform translational and rotational motions in the field of solar attraction. Let’s assume that the observer on the surface of the planet, knows (even approximately) an orbit and variations of orientation. It is necessary to clarify the motion of the instanteous rotation axis on the planet’s surface from the observer’s point of view on the planet’s surface. 1. The coordinate system, to describe the translational and rotational motions of planets around the Sun we shall take into account the properties of orbits of solar system planets, namely: 1) All planets move in the same direction as the Sun revolves. 2) At the present time, from June until December the Earth’s inhabitants see the north pole of the Sun and during the second half of year the southern one (Beleckei 1975, Menzel 1959).