Multicolour CCD photometry of old open clusters:

\n We present multicolour CCD photometry for two poorly \nstudied open clusters \n(King 5 and Be 20). Photometry for a field near King 5 was also \ncarried out to estimate the contamination by field stars. \n The colour magnitude diagrams (CMD) of the clusters show a well \ndefined main sequence extending to the limit of the photometry, $V \n\\approx20$ mag. The reddening for King 5, estimated from the \ncolour-colour diagram, is ~0.82, whereas that for \nBe 20 as estimated by comparing theoretical main-sequence (MS) with the \nobserved MS is 0.10. The morphology of the CMDs indicates that these \nclusters are old. The \nCMD of Be 20 shows a globular cluster-like horizontal branch. \nIn case of King 5 the comparison of \nobservational CMDs with the standard isochrones of VandenBerg \n([CITE]) indicates an apparent discrepancy between the shape of the turnoff \nand isochrones.\nThe CMDs of King 5 seem to be better understood in terms of stellar models with convective overshoot. \nThe comparison of the CMDs with the stellar models by Bertelli et al. ([CITE]) \nwith convective overshoot produces a good fit for a metallicity $Z = 0.008$ \nand an age = 1 Gyr for King 5 and 5 Gyr for Be 20. An apparent distance modulus $(m-M) = 14.0$ and \n15.1 has been estimated for King 5 and Be 20 respectively. They \ncorrespond to a distance of $1900 \\pm100$ pc and 9026 ± 480 pc, \nrespectively. The radial density distribution in King 5 indicates \n\tthat there is an excess of low mass stars in the outer region of the \n\tcluster, whereas the density distribution in Be 20 shows a good fit with \nthe empirical King ([CITE]) model. For both clusters, observations have also been carried out to \nsearch for variable stars.\n\n\n