The heavy elements mixture and the stellar cluster age
  Recent analyses of solar spectroscopic data (see Asplund, Grevesse & Sauval 2004 and references therein) suggest a significative variation of the heavy elements abundance. The change of heavy mixture might affect the determination of the clusters age for two different reasons: the change of theoretical isochrones at fixed metallicity and the variation of the inferred cluster metallicity from the observed [Fe/H]. The first point is analyzed discussing the effects of updating the metal distribution on theoretical evolutionary tracks and isochrones for metallicities suitable for the galactic globular and open clusters and for the bulk population of the Large Magellanic Clouds. The maximum variation of the estimated age ($\approx$0.5 Gyr), although not negligible, is still within the present uncertainty. The second point is addressed by comparing present theoretical predictions with the very precise observational data of the Hyades cluster from the Hypparcos satellite. 
S. Degl'Innocenti, P.G. Prada Moroni and B. Ricci (University and INFN   of Pisa and University and INFN Ferrara, Italy)