  We constrain the mass-to-light ratios, gas mass fractions, baryon mass
fractions and the ratios of total to luminous mass for a sample of eight nearby
relaxed galaxy groups and clusters: A262, A426, A478, A1795, A2052, A2063,
A2199 and MKW4s. We use ASCA spatially resolved spectroscopic X-ray
observations and ROSAT PSPC images to constrain the total and gas masses of
these clusters. To measure cluster luminosities we use galaxy catalogs
resulting from the digitization and automated processing of the second
generation Palomar Sky Survey plates calibrated with CCD images in the
Gunn-Thuan g, r, and i bands.
  Under the assumption of hydrostatic equilibrium and spherical symmetry, we
can measure the total masses of clusters from their intra-cluster gas
temperature and density profiles. Spatially resolved ASCA spectra show that the
gas temperature decreases with increasing distance from the center. By
comparison, the assumption that the gas is isothermal results in an
underestimate of the total mass at small radii, and an overestimate at large
cluster radii.
  We have obtained luminosity functions for all clusters in our sample. After
correcting for background and foreground galaxies, we estimate the total
cluster luminosity using Schechter function fits to the galaxy catalogs. In the
three lowest redshift clusters where we can sample to fainter absolute
magnitudes, we have detected a flattening of the luminosity function at
intermediate magnitudes and a rise at the faint end. These clusters were fit
with a sum of two Schechter functions. The remaining clusters were well fit
with a single Schechter function.
