STELLAR EVOLUTION MODELS FOR Z = 0.0001 TO 0.03

We have calculated a grid of empirically well tested evolutionary trac ks with masses M between 0.5 and 50M., spaced by approximately 0.1 in log M, and with metallicities Z = 0.0001, 0.0003, 0.001, 0.004, 0.01, 0.02 and 0.03. We use a robust and fast evolution code with a self-ada ptive non-Lagrangian mesh, which employs the mixing-length theory but treats convective mixing as a diffusion process, solving simultaneousl y for the structure and the chemical composition. The hydrogen and hel ium abundances are chosen as functions of the metallicity: X = 0.76 - 3.0Z and Y = 0.24 + 2.0Z. Two sets of models were computed, one withou t and one with a certain amount of enhanced mixing or 'overshooting'. This amount has been empirically chosen by means of various sensitive tests for overshooting: (1) the luminosity of core helium burning (blu e loop) giants of well-known mass, (2) the width of the main sequence as defined by double-lined eclipsing binaries with well-measured masse s and radii, and (3) the shape and implied stellar distribution of iso chrones of various open clusters. The first two tests have been the su bject of previous papers, the third test is discussed in this paper. O n the basis of these tests, we recommend the use of the overshooting m odels for masses above about 1.5 M.. We describe here the characterist ics of the models, the procedure for constructing isochrones for arbit rary age and metallicity from the models, and the performance of these isochrones for several intermediate-age and old open clusters. All or iginal models are available in electronic form and we describe the mea ns by which they may be obtained.