  We analyze a sample of 105 clusters having virial mass homogeneously
estimated and for which galaxy magnitudes are available with a well defined
high degree of completeness. In particular, we consider a subsample of 89
clusters with B_j band galaxy magnitudes taken from the COSMOS/UKST Southern
Sky Object Catalogue. We compute cluster luminosities L_{B_j} within several
clustercentric distances and within the virialization radius R_{vir}. In
particular, we use the luminosity function and background counts estimated by
Lumsden et al. (1997) on the Edinburgh/Durham Southern Galaxy Catalogue. We
analyze the effect of several uncertainties connected to photometric data,
fore/background removal, and extrapolation below the completeness limit of the
photometry, in order to assess the robustness of our cluster luminosity
estimates. We draw our results on the relations between luminosity and
dynamical quantities from the COSMOS sample by considering mass and
luminosities determined within the virialization radius. We find a very good
correlation between cluster luminosity, L_{B_j}, and galaxy velocity
dispersion, sigma_v, with L_{B_j} proportional to sigma_v^{2.1--2.3}. Our
estimate of typical value for the mass-to-light ratio is M/L_{B_j} about 250
(in solar units). We do not find any correlation of M/L_{B_j} with cluster
morphologies, i.e. Rood--Sastry and Bautz--Morgan types, and only a weak
significant correlation with cluster richness. We find that mass has a slight,
but significant, tendency to increase faster than the luminosity does, M
proportional to L_{B_j}^{1.2--1.3}. We verify the robustness of this relation
against a number of possible systematics.
