One of the fundamental problems of lunar astronomy is the reduction of the coordinates of the Moon's surface, found by astronomical methods, to its mean pole. The instantaneous poles of the rotation axis and the instantaneous equator move in the Moon's body. The unstable position of this equator does not allow one to use in selenodesy the instantaneous spherical coordinates which have not been preliminarily transformed into some unified system of coordinates. Such a reduction can be made to the system of coordinates connected with the mean pole—to be definite, we shall speak about the Moon's North pole.