CCD PHOTOMETRY OF THE OLD OPEN CLUSTER 092-SC18

We present deep VIc CCD photometry for the open cluster 092-SC18 colle cted at the CTIO 1.5 meter telescope in April, 1994 as part of a progr am of photometric studies of old open clusters. VandenBerg (1985) isoc hrone fits to a V, V-I color-magnitude diagram yield estimates of clus ter parameters of 4-6 Gyrs, with a range in metallicity of -0.23 to -0 .75 dex. Based on the best fit isochrone, 092-SC18 is 5 Gyrs old, has an abundance of [Fe/H] = -0.45 dex, reddening of E(V-I) = 0.32, and (m -M)(0) of 14.88 mag. With the current determination of the cluster's d istance modulus, 092-SC18 is at a distance of 9.5 kpc, with a Galactoc entric radius of 10.5 kpc, and lies 1.2 kpc below the Galactic plane. By extrapolating the main-sequence mass calculations to low-mass stars and accounting for a typical concentration of binaries, we place a lo wer limit to the cluster mass of similar to 4200 M.. From an exponenti al fit to the stellar surface density of the cluster field, we find a linear diameter of 18 pc for 092-SC18. (C) 1996 American Astronomical Society.