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.

ABSTRACT
Ⅰ. INTRODUCTION
Ⅱ. SELECTION OF CLUSTERS
Ⅲ. BASIC PHOTOMETRIC DATA
Ⅳ. DERIVATION OF SOME PHYSICAL QUANTITIES
Ⅴ. LUMINOSITY FUNCTIONS AND MASS FUNCTIONS
Ⅵ. CONCLUSIONS
REFERENCES

• LEE HYUN SOOK(Department of Astronomy, Seoul National University)
• LEE SEE-WOO(Department of Astronomy, Seoul National University)