Here is some recent information on OC.
Astrophysical parameters of Galactic open clusters.
KHARCHENKO N.V., PISKUNOV A.E., ROESER S., SCHILBACH E. and SCHOLZ R.-D.
http://simbad.u-strasbg.fr/simbad/si...6A...438.1163K
Abstract
We present a catalogue of astrophysical data for 520 Galactic open clusters. These are the clusters for which at least three most probable members (18 on average) could be identified in the ASCC-2.5, a catalogue of stars based on the Tycho-2 observations from the Hipparcos mission. We applied homogeneous methods and algorithms to determine angular sizes of cluster cores and coronae, heliocentric distances, mean proper motions, mean radial velocities, and ages. For the first time we derive distances for 200 clusters, radial velocities for 94 clusters, and ages of 196 clusters. This homogeneous new parameter set is compared with earlier determinations, where we find, in particular, that the angular sizes were systematically underestimated in the literature.
http://adsabs.harvard.edu/cgi-bin/bi...%2E438%2E1163K