Аннотация:We report on multicolor UBVRI photometry of SS 433 during two eclipses. The goal of this work is to reconstruct the spectral energy distribution (SED) in and out of eclipse in order to extract some flux components including that from the eclipsed central source and that from the donor star. By combining the observed flux of the donor with the derived extinction and known distance, the absolute magnitude of the donor was estimated. Then by assuming a mass - luminosity relation, the donor mass is determined. Finally, adopting a mass ratio from an analysis of the X-ray light curve, a mass for the compact companion is found to be close to 1.4 solar masses, so that it might be identified as a neutron star. The complete paper has been published in Variable Stars Vol. 31, No.5 (2011).