Proper motions of stars in NGC 2286

The plates have the maximum epoch difference of some 70 years and were taken with the double astrograph at Zo-Se station of Shanghai Observatory, which has an aperture of 40 cm, a focal length of 6.9 m and a scale of 30 arcsec/mm.

The number of stars with membership probabilities higher than 0.7 and radial distances from the cluster centre less than 12' is 90. The average standard errors of proper motions vary from +/-0.0007"/yr for bright stars in the inner part of the field to some +/-0.0016"/yr for faint stars in the outer part of the field, and are statistically dependent on the number of measured plates per star. It is found from an analysis of the surface number density distribution of cluster members that the angular radius of NGC 2286 is some 12' and the corresponding linear radius 4.5 pc.