MULTICOLOR PHOTOMETRY OF CLUSTERS OF GALAXIES - A3284, A3305, A1942

We present complete multicolor photometry in the Gunn system for the t hree clusters of galaxies A3284, A3305 and A1942 at redshift z similar to 0.2. INVENTORY magnitudes and colours have been obtained for over 1,000 objects in the three fields down to g = 24, and with a good comp leteness level in the detections (85% or better) about one magnitude b righter. By fitting with King profiles the r counts we derived the tot al number of galaxies and the core radius down to the r magnitude limi t in each cluster. These are N-TOT = 146 galaxies and R(c) = 0.24 Mpc for A3284, N-TOT = 129 and R(c) = 0.20 Mpc for A3305, N-TOT = 130 and R(c) = 0.24 Mpc for A1942. The observed mean redshift of the clusters is z = 0.150 +/- 0.001 for A3284, z = 0.157 +/- 0.001 for A3305, and z = 0.226 +/- 0.001 for A1942. The c-m diagrams and the g-i colour dist ribution as well as the two-colour diagrams are used to single out ear ly-type galaxies and spirals on the basis of their different photometr ic properties. This approach aimed at a self-consistent classification of galaxies on the basis of photometric indicators will be further de veloped for a systematic study of the galaxy population in distant clu sters.