Context : The last decade showed an impressive observational effort from the photometric and spectroscopic point of view for ancient stellar clusters in our Galaxy and beyond , leading to important and sometimes surprising results .

Aims : The theoretical interpretation of these new observational results requires updated evolutionary models and isochrones spanning a wide range of chemical composition so that the possibility of multipopulations inside a stellar cluster is also taken also into account .

Methods : With this aim we built the new “ Pisa Stellar Evolution Database ” of stellar models and isochrones by adopting a well-tested evolutionary code ( FRANEC ) implemented with updated physical and chemical inputs .
In particular , our code adopts realistic atmosphere models and an updated equation of state , nuclear reaction rates and opacities calculated with recent solar elements mixture .

Results : A total of 32646 models have been computed in the range of initial masses 0.30 \div 1.10 M _ { \sun } for a grid of 216 chemical compositions with the fractional metal abundance in mass , Z , ranging from 0.0001 to 0.01 , and the original helium content , Y , from 0.25 to 0.42 .
Models were computed for both solar-scaled and \alpha -enhanced abundances with different external convection efficiencies .
Correspondingly , 9720 isochrones were computed in the age range 8 \div 15 Gyr , in time steps of 0.5 Gyr .
The whole database is available to the scientific community on the web .
Models and isochrones were compared with recent calculations available in the literature and with the color-magnitude diagram of selected Galactic globular clusters .
The dependence of relevant evolutionary quantities , namely turn-off and horizontal branch luminosities , on the chemical composition and convection efficiency were analyzed in a quantitative statistical way and analytical formulations were made available for reader ’ s convenience .
These relations can be useful in several fields of stellar evolution , e.g .
evolutionary properties of binary systems , synthetic models for simple stellar populations and for star counts in galaxies , and chemical evolution models of galaxies .

Conclusions :