Study of Old Open Clusters NGC 1605, Czernik 18, NGC 2509

Abstract

We present the first CCD photometric UBVRI observations of three open clusters NGC 1605 (OCI 406), Czernik 18 (OCI 426) and NGC 2509 (OCI 630) obtained by using the 1.02 m telescope at Vainu Bappu Observatory, Kavalur. While the colour excell E(B-V) for the cluster OCI 426 is found to be 0.43 mag, it is estimated to be 0.14 mag for OCI 406 and 0.15 mag for OCI 630. After correcting for these colour excesses, their distances are found to be 1148 pc (OCI 406), 955 pc (OCI 426), and 912 pc (OCI 630). Further, as the ages of these clusters are found to be in the range of 0.8 x 109 yrs to 8 x 109 yrs, they may be categorised as old open clusters.