  We present a detailed analysis of the cluster of galaxies \a4. The optical
data include a redshift catalogue of 466 galaxies, out of which 274 belong to
the main cluster and a CCD photometric catalogue in a much smaller region, with
239 and 610 galaxies in the V and R bands respectively. The X-ray analysis is
based on an image obtained with the ROSAT PSPC. Besides Abell 496 itself, the
velocity distribution along the line of sight shows the existence of at least
four structures at different redshifts, one of them seeming to be a poor
cluster at a velocity of 30083 km/s. The other of these structures have a too
large spatial extent to be clusters but may be filaments along the line of
sight or other young structures. Various independent methods show that Abell
496 appears to be a quite relaxed cluster, except perhaps for the distribution
of emission line galaxies. These appear to be distributed in two samples
falling on to the main cluster, one from the back (the ELGs concentrated
towards the west) and one from the front (the high velocity ELGs). The bright
part of the galaxy luminosity function, built from the redshift catalogue,
shows a flattening at R$\sim 16$ (M$_{\rm R}\sim -20.5$), and can be accounted
for by a gaussian distribution of bright galaxies and a power law or Schechter
function for faint galaxies. The deeper galaxy counts derived from CCD imaging
show a dip at R$\sim 19.5$ (M$_{\rm R} \sim -17$) which can be modelled
assuming a cut-off in the luminosity function such as that observed in Coma. We
propose a model for the X-ray gas and derive the galaxy, X-ray gas and total
dynamical masses, as well as the baryon fraction in the cluster. \a4 appears as
a relaxed cluster which can be used as a prototype for further studies.
