NGC 2587: a sparse open cluster projected onto a populous star field

We present CCD BVIKC photometry in the field of the open cluster NGC 2587. We developed a new method to clean statistically the colour-magnitude diagrams. NGC 2587 is found to be slightly younger than the Hyades and probably of solar metallicity. From 18 probable members with measured proper motions, we derived the following mean cluster values: Ha = —4.3 ± 3.6 mas yr_1 and ^ = —2.5 ± 3.4 mas yr_1. Colour excesses, E(B — V) = 0.10 and E(V — I) = 0.15 mag, and a heliocentric distance of 3.7 ± 0.7 kpc are obtained. The interstellar extinction in the cluster direction is found to follow the normal reddening law.