Two intermediate age open clusters: NGC 752 and NGC 3680.

In this paper, with the aid of synthetic color-magnitude diagram (CMD) technique we study two scarcely populated and slightly metal-poor intermediate age open clusters, namely NGC 752 and NGC 3680. The analysis is made using both standard and overshoot models calculated by the Padova group (Fagotto 1990; Alongi et al. 1991, 1993). The advantage with the synthetic CMD technique is that it allows for quantitative predictions for the star counts and luminosity functions. Adopting the metallicity indicated for each cluster by current determinations, we seek to determine the color excess, distance modulus, and age at the same time. Looking at the fit of the whole CMD, the behaviour of the main sequence stars LF, and two suitable ratios of star counts we try to discriminate between the two evolutionary schemes. We suggest that models with convective overshoot ought to be preferred to the classical ones.