The relatively young, metal-poor and distant open cluster NGC 2324

We have obtained CCD photometry in the Johnson V, Kron-Cousins I and CT1 Washington systems for NGC 2324, a rich open cluster located similar to35degrees from the Galactic anticentre direction. We measured V magnitudes and V - I colours for 2865 stars and T, magnitudes and C - T, colours for 1815 stars in an area of 13.'6 x 13.'6. The comparison of the cluster colour-magnitude diagrams with isochrones of the Geneva group yield E(V - I) = 0.33 +/- 0.07 and V - M-V = 13.70 +/- 0.15 for log t = 8.65 (t = 440 Myr) and Z = 0.008 ([Fe/H] = -0.40), and E(C - T-1) = 0.40 +/- 0. 10 and T-1 - My(T1) = 13.65 +/- 0.15 for the same age and metallicity level. The resulting E(V - 1) reddening value implies E(B - V) = 0.25 +/- 0.05 and a distance from the Sun of (3.8 +/- 0.5) kpc. Star counts carried out within and outside the cluster region allowed us to estimate the cluster angular radius as 5.'3 +/- 0.'3 (5.9 pc). When using the E(B - V) reddening value here derived and the original Washington photometric data of Geisler et al. (199 1) for the stars confirmed as red cluster giants from Coravel radial velocities, we found [Fe/H] = -0.31 +/- 0.04, which is in good agreement with the best fits of isochrones. Therefore, NGC2324 is found to be a relatively young, metal-poor and distant open cluster located beyond the Perseus spiral arm. A comparison of NGC 2324 with 10 well-known open clusters of nearly the same age shows that the cluster metal abundance and its position in the Galaxy are consistent with the existence of a radial abundance gradient of -0.07 dex kpc(-1) in the Galactic disc.