Alessandra Celletti, Gabriella Pinzari Four classical methods for determining planetary elliptic elements: a comparison (1106K, Postcript) ABSTRACT. The discovery of the asteroid Ceres by G. Piazzi in 1801 motivated the development of a mathematical technique proposed by C.F. Gauss, which allows to recover the orbit of a celestial body starting from a minimum of three observations. Here we compare the method proposed by Gauss with the techniques (based on three observations) developed by P.S. Laplace and by O.F. Mossotti. We also consider another method developed by Mossotti, based on four observations. We provide a theoretical and numerical comparison among the different procedures. As an application, we consider the computation of the orbit of the asteroid Juno.