The selenopotential was determined at the Apollo 12 landing site (A12) using the selenocentric constant, Stokes' constants of the Moon up to n=13, the angular velocity of rotation of the Moon and the value of gravity directly observed at A12. Using and the constants mentioned above, the radius-vector of the equiselenopotential surface passing through A12 was derived. The fundamental selenocentric parameters, based on this surface, were computed, as well as the deflections of the vertical especially in some strongly anomalous regions of the Moon. For some mascons an elementary interpretation has been carried out.