Detailed analysis of six F and G dwarfs in the Pleiades and fourteen in the Hyades indicates that the Fe/H ratio in the Hyades is 50 percent higher than that in the Pleiades, the latter yielding the solar value. To gain insight into the cause of the differences in observed narrow-band photometric indices between the clusters, a grid of blanketed model atmospheres was computed. The models provide estimates of the changes in the Stro"mgren four-color indices caused by variations in the metal abundance z and the microturbulent velocity . The trajectories in the (w1, b - y)-plane resulting from either of these variations are similar and difficult to distinguish observationally. The trajectories in the (c1, b - plane, however, differ significantly, and in some cases this may permit these two atmospheric parameters to be distinguished by the photometry alone. In the case of the Pleiades and Hyades, it appears that the observed differences in and can explain the photometric differences between the clusters. However, the effects of initial helium content and stellar evolution considerably complicate the interpretation of the diagrams of these clusters; interpretation is even more difficult for more heterogeneous samples of stars.
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H. et al. (1971) studied this question.