  We present magnitudes and redshifts of galaxies in the cluster of galaxies
CL0017-20 and in the double cluster CL0500-24. Luminosity functions and
velocity distributions have been derived. CL0017-20 possesses a virial mass of
$2.9 \times 10^{14}$ M$_\odot$ and a \vmag band luminosity of $2.3 \pm 0.5
\times 10^{12}$ L$_\odot$ ($M/L_{\rm V} = 127$), much of it in a very compact
core of size 113 kpc. Our new velocities and photometry of CL0500-24 confirm
its double nature. Our group algorithm clearly detects two subconcentrations
with masses 1.9 and $2.2 \times 10^{14}$ M$_{\odot}$. Its total \vmag band
luminosity amounts to $2.7 \pm 0.8 \times 10^{12}$ L$_{\odot}$ ($M/L_{\rm V}$
of 157). Since the crossing and collapse times in both clusters are smaller
than the age of the Universe, they appear bound and virialized. It is
surprising that although $M/L$ is small in these clusters, giant arcs have been
detected in both.
