NGC 2236: a moderately metal‐poor open cluster of Hyades‐like age located beyond the Perseus spiral arm

New CCD photometry in the Washington system C and T 1 passbands down to T 1 ∼ 18.5 mag in the field of the northern open cluster NGC 2236 is presented. T 1 magnitudes and C − T 1 colours for a total of 1162 stars within an area of 13.6 × 13.6 arcmin 2 were measured. These CCD data were supplemented with photoelectric CMT 1 T 2 photometry of 13 red giant candidates. The comparison of the cluster ( T 1 , C − T 1 ) colour–magnitude diagram with theoretical isochrones computed for the Washington system yields E ( C − T 1 ) = 1.10 ± 0.10 and for log t = 8.80  ( t = 600 +100 −40   Myr) and Z = 0.008 . The derived E ( C − T 1 ) value implies E ( B − V ) = 0.55 ± 0.05 . NGC 2236 is then located at 2.5 ± 0.5 kpc from the Sun beyond the Perseus spiral arm and at ∼10.8 kpc from the Galactic centre. A cluster angular diameter of 9.4 arcmin, equivalent to 6.8 pc, was estimated from star counts both within and outside the cluster field. We also derived from the stellar density profile a cluster core radius of r c = 1.7 arcmin (1.2 pc) and an annular corona of Δ r c = 1.8 r c (2.2 pc). Five independent Washington abundance indices yield a mean cluster metallicity of [Fe/H]=−0.3 ± 0.2, which is not only in reasonably good agreement with the one obtained from the isochrone fit, but also compatible with the existence of a radial abundance gradient in the Galactic disc. We examined the properties of a sample of 20 known open clusters aligned along the line‐of‐sight to NGC 2236. Berkeley 27 appears as the farthest and oldest cluster of the studied sample.