SCHMIDT SURVEY IN THE GALACTIC ANTICENTRE DIRECTION .1. INVESTIGATIONOF OPEN CLUSTERS

A study of four open clusters in the direction of the Galactic anticen tre (l = 186 degrees, b = +2 degrees) is presented. In a field of 8.32 square degrees proper motions and B magnitudes for about 79000 stars down to 19.5 were determined on Tautenburg Schmidt plates. For more th an 15 500 of them U magnitudes down to 17.3 could be obtained. Additio nally, OCA Schmidt plates were used to determine V, R magnitudes in a larger field of 24.45 square degrees for 271000 stars down to V = 18.2 . For stars brighter than V = 15.5 an accuracy of about 1.5 mas/yr has been estimated for proper motions. The rms errors of stellar magnitud es and colour indices are 0.09 - 0.12 mag. Several open clusters have been already known in this direction of the sky, e.g. NGC 2168 or M 35 (C 0605+243), NGC 2158 (C 0604+241) and IC 2157 (C 0601+240). Inspect ing the plates and analysing the colour-magnitude diagrams and publish ed data, we could identify an additional anonymous cluster C 0605+242 with a projection on the sky near the centre of M 35 but at a larger d istance from the Sun. The cluster membership determination was carried out using information on spatial and proper motion distributions of s tars in the field. The colour-magnitude diagrams were derived down to the limiting stellar magnitude. For each cluster the interstellar exti nction Av, the diameters of the core and corona, the ages and spatial velocity components (V,W) relative to the LSR in the Y,Z - Galactic di rections were determined. The distances to the clusters of 960 pc, 260 0 pc, 2520 pc and 3700 pc were obtained for M 35, IC 2157, C 0605+242 and NGC 2158. They show the loci of the clusters in the Local and Pers eus spiral arms and at external border of Perseus arm, respectively.