2005AJ....129..872A

CCD photometry on the intermediate-band uvbyCaHβ system is presented for the metal-deficient open cluster NGC 2243. Restricting the data to probable single members of the cluster using the color-magnitude diagram (CMD) and the photometric indices alone generates a sample of 100 stars at the cluster turnoff. The average E(b-y)=0.039±0.003 (s.e.m.) or E(B-V)=0.055±0.004 (s.e.m.), where the errors refer to internal errors alone. With this reddening, [Fe/H] is derived from both m₁and hk, using b-y and Hβ as the temperature index. The agreement among the four approaches is excellent, leading to a final weighted average of [Fe/H]=-0.57±0.03 (s.e.m.) for the cluster, on a scale where the Hyades has [Fe/H]=+0.12. Using a combination of photometric and spectroscopic data, 27 probable cluster members are identified and used to delineate the red giant branch and a well-defined clump at V=13.70, while eliminating the so-called second clump at V=14.1. Interpolation between isochrones of appropriate [Fe/H] leads to an apparent modulus of m-M=13.15±0.1 and an age of 3.8±0.2 Gyr. A differential CMD comparison with Ber 29, a cluster with a galactocentric distance almost twice that of NGC 2243, constrains Ber 29 to be at least as young and as metal-rich as NGC 2243.