This is the first of a series of three papers devoted to the calibration of a few parameters of crucial importance in the modeling of the evolution of intermediate-mass stars , with special attention to the amount of convective core overshoot .
To this end we acquired deep V and R photometry for three globular clusters of the Large Magellanic Cloud ( LMC ) , namely NGC 2173 , SL 556 and NGC 2155 , in the age interval 1–3 Gyr .
In this first paper , we describe the aim of the project , the VLT observations and data reduction , and we make preliminary comparisons of the color-magnitude diagrams with both Padova and Yonsei-Yale isochrones .
Two following papers in this series present the results of a detailed analysis of these data , independently carried out by members of the Yale and Padova stellar evolution groups .
This allows us to compare both sets of models and discuss their main differences , as well as the systematic effects that they would have to the determination of the ages and metallicities of intermediate-age single stellar populations .