Positional photographic observations of Saturn, Uranus, Neptune, their satellites and Pluto in 1990 with the telescope ZTA-2.6 m at Byurakan in Armenia

The experimental astrometrical observations in the main focus of the high-lightpower telescope ZTA-2.6 m at Byurakan observatory have been carried out with the aim of providing precise coordinates of the outer planets and their satellites. 5 nights were used for the observations and 38 plates with about 150 images of planets and their satellites were obtained. The "two-step" method of reduction was applied with the FOCAT-S catalogue as a basis. The mean error is ±(0.24 - 0.56) for a single "Satellite minus Satellite" or "Satellite minus Planet" measurement. A strong distorsion of the projection was found in the astrometric treatment of the plates, with the magnitude of the order of 8 × 10-6 mm-2.