LUMINOSITY FUNCTIONS AND MASS FUNCTIONS OF EIGHT OPEN CLUSTERS

The well observed 8 open clusters, NGC 6530, 2264, 654, 129, 2168, Pleiades, Praesepe and Hyades were selected on the basis of photometric observation and proper motion study. The luminosity functions (LF) and mass functions (MF) of these clusters are different with cluster age and they could be divided into three age groups (t<$10^7$ yrs, $10^7$$10^8$ yrs, $10^8$$10^9$ yrs). From these LF's and MF's, the mean LF and MF of the open clusters are derived and these functions suggest the time-dependent initial mass function (IMF) and the variation of observed MF with cluster age.