We present UBV CCD photometry of the double cluster NGC 1850 located at the NW edge of the bar of the Large Magellanic Cloud. The color-magnitude diagram shows that NGC 1850 has a prominent population of massive core-He burning stars which is incomparably richer than any other known star clusters. The reddening is estimated from the (U-B) - (B-V) diagram to be E(B - V) = 0.15±0.05. We have estimated the ages of NGC 1850 and a very compact blue star cluster (NGC 1850A) located at ~30" west of NGC 1850 using isochrones based on the convective overshooting models: 80 ±10 Myrs and 5 ± 2 Myra, respectively. Several evidence suggest that it is probably the compact cluster NGC 1850A that is responsible for the arc-shaped nebulosity (Henize N 103B) surrounding the east side of NGC 1850.

• Lee Myung-Gyoon(Department of Astronomy, Seoul National University)