Photographic observations of Pluto 1991-1994 with the Baldone Schmidt telescope

¹ Central Astronomical Observatory of the Russian Academy of Sciences at Pulkovo, Pulkovskoe sh. 65/1, Saint-Petersburg, 196140, Russia e-mail: vryl@pulvz.spb.su
² Radioastrophysical Observatory, Latvian Academy of Sciences, Turgeneva 19, Riga, LV-1527, Latvia

Send offprint request to: V.P. Ryl'kov

Received: 6 June 1995
Accepted: 21 December 1995

Abstract

55 photographic positions of the Pluto for 1991-1994 are presented. The observations were carried out by Latvian astronomers using the 80/120/240 cm Schmidt telescope at Baldone near Riga. 34 plates were reduced by using the 12-21 reference stars from catalogue of southern stars FOCAT-S, created at Pulkovo. The mean reduction errors vary from 0.23″ to 0.34″ for both coordinates. The obtained Pluto positions were compared with the ephemeris JPL DE200. The increase of the mean (O-C) residuals in RA, already noticed in previous works by the Pulkovo authors, is confirmed. In 1994 the (O-C) residuals with respect DE200 have reached 2.32″ ±0.07″ in RA and -0.74″ ±0.07″ in Dec.