The luminosity function of MS 2255.7+2039 at z=0.288

The luminosity function of MS2255.7+2039 at z = 0.288 is determined down to a total magnitude of R similar to 24, corresponding to M-R similar to -17( H-0 = 50 km s(-1) Mpc(-1)). The data are corrected for incompleteness and c rowding using detailed simulations. We find that the luminosity function is steeper than a standard Schechter function at faint magnitudes, and shows an excess of galaxies below M-R similar to -19. After corrections for light loss and crowding, the data can be described by a sum of two Schechter fun ctions, one with M-R* = -22.8 and alpha = -1.0, and one steeper with M-R* = -18.9 and alpha = -1.5, representing the dwarf population. A straight-line fit to the faint part yields a slope similar to the Schechter alpha = -1.5 of the dwarf population. The luminosity function of MS2255.7+2039 is compa red to other clusters at lower redshifts, and does not show any significant difference. The redshift range for clusters in which increased number of d warf galaxies have been found is therefore extended to higher redshifts.