Red-Sequence Galaxies with young stars and dust The cluster A901/902 seen with COMBO-17 Christian Wolf (Oxford) Meghan E. Gray (Nottingham) Klaus Meisenheimer (Heidelberg) A&A, in press A901a A901b A902 Testing ground: the A901/902 supercluster z=0.16: ~5x5 Mpc COMBO-17 SEDs SED classification ~98% complete at R