Four-colour and H-beta photometry for low mass members in open clusters. I. The Praesepe.

The uvby and H-beta photometry has been obtained for 32 stars in the Praesepe cluster. The stars observed were chosen from the proper motion study of Jones and Cudworth (1983), with colors ranging between 0.4 and 0.6 in (b-y), and are thus mostly G and K members of the lower main sequence. The related photometric diagrams give values of distance modulus and metal contents compatible with common accepted values. The c1-(b-y) diagram shows the lack of the Hyades anomaly in the K star range.