The Colour-Magnitude Relation and the Age of Galaxies in the Cluster AC118 at z=0.31

We derive the Colour-Magnitude (CM) relation for the galaxy cluster AC118 at z=0.31 and use this relation to set constraints on the formation epoch and on the age spread of cluster galaxies in the framework of the passive evolution scenario. This work is based on observations at ESO NTT (OAC guaranteed time).