Stellar clusters are crucial in the study of a variety of topics including the star formation process, stellar nucleosynthesis and evolution, dynamical interaction among stars, or the assembly and evolution of galaxies. In particular, Open Clusters (OCs) have been widely used to constrain the formation and evolution of the Milky Way disc. They provide information about the chemical patterns and the existence of radial and vertical gradients or an age-metallicity relation. However, all these investigations are hampered by the fact that only a small fraction of clusters have been studied homogeneously. Galactic surveys performed from the ground such as the Apache Point Observatory Galactic Evolution Experiment (APOGEE), the Gaia-ESO Survey (GES), or the GALactic Archaeology with HERMES (GALAH) include OCs among their targets. OCs are also sampled from the space by the Gaia and Kepler missions.

The OCCASO goal is to derive abundances for more than 20 chemical species in at least 6 Red Clump stars in ∼30 Northern hemisphere OCs. In order to ensure the reliability of the derived chemical abundances, these are derived using different analysis techniques similar to what is being performed by GES.

One of the OCCASO requirements is the homogeneity between instruments, methods and model atmospheres used, and in the same scale than the GES-UVES abundances. For this reason we are performing different tests checking internal and external consistency. Derived stellar atmosphere parameters and Fe abundances will be published in the first data release scheduled for the first semester of 2015.

The online pdf of the poster with first results is available at https://gaia.ub.edu/Twiki/pub/GREATITNFC/ProgramFinalconference/poster_OCCASO.pdf.