  Recent X-ray observations of the rich galaxy cluster CL 0939+4713 at z = 0.41
with the ROSAT/HRI as well as with the ASCA/GIS and ASCA/SIS are presented and
analysed. With the high resolution imaging data we confirm and extend the
earlier impression that the cluster has a lot of substructure. Two maxima of
the cluster emission are obvious in the images, each of them shows even some
internal structure. For the total luminosity of the cluster in the ROSAT band
we obtain L = 6.4_{-0.3}^{+0.7} 10^{44} erg/s. We perform spectral fits for the
two ASCA instruments and for the ROSAT/PSPC simultaneously. The most reliable
numbers for the temperature and metallicity for the intracluster gas are T =
7.6^{+2.8}_{-1.6} keV and m = 0.22^{+0.24}_{-0.22} Msol, respectively. We find
a relatively small total mass, a small gas mass ratio and a small iron mass to
light ratio. These numbers together with relatively low luminosity for such an
optically rich cluster and the pronounced substructure confirm that CL
0939+4713 is a young cluster still far away from a virialised state.
  In the same ROSAT/HRI image the X-ray emission of a background quasar (z
\approx 2) can clearly be identified. With a luminosity of L \approx 1.4
10^{45} erg/s it belongs to the X-ray brightest quasars. A striking difference
between the ROSAT/PSPC and the ROSAT/HRI observations (taken almost five years
apart) is the fainting of one X-ray source RXJ0943.0+4701 by at least a factor
of ten. We try to identify this source from deep optical data. Our best
candidate is a blue compact object, possibly an AGN.
