... Astrometric Observations of the Second, Third, and Fourth Satellites of Uranus I. S. Izmailova, S. A. Korotkiib, M. V. Ereshkob, and A. V. Stepurab a Pulkovo Observatory of the Russian Academy of Sciences, Pulkovskoe shosse 65­1, St. Petersburg, 196140 Russia b Ka-Dar Observatory, 1-i Neopalimovskii per., ... ASTROMETRIC OBSERVATIONS 43 To determine the center coordinates and other parameters of a satellite or a star image, we solved a redundant system with the nonlinear least-squares method. ...