  Using two epochs of observations with HST/WFPC2 we obtain the stellar proper
motions for all stars in the field. The proper motions are used to separate the
bulge from the cluster stars. The stellar sequences in the resulting colour-
magnitude diagram (CMD) are better defined than in any previously published
CMD. Using alpha-enhanced stellar isochrones we find NGC 6528 to have a
probable age of 11+-2 Gyrs, this is the first attempt to establish the absolute
age for NGC6528. Previous studies have only compared the fiducial ridge line
for the cluster to that of other globular clusters of similar metallicities.
Mainly the comparisons have been with regards to NGC6553 and 47Tuc. With the
new metallicity determinations for individual stars in both NGC6553 and NGC6528
it is now clear that 47Tuc (at -0.71 dex) has a significantly lower metallicity
than NGC6528 and NGC6553 and is thus not a suitable comparison cluster as
regards differential age determinations. A comparison with the fiducial line
for NGC6553 confirms results in earlier studies, e.g. Ortolani et al. (1995),
that the two clusters indeed have very similar ages. From the measured
velocities both the proper motion of the cluster and the velocity dispersion in
the Galactic bulge are found. NGC 6528 is found to have a proper motion
relative to the Galactic bulge of mu_l=0.006 and mu_b=0.044 arcsec per century.
Using stars with ~14 < V < 19 (i.e. the red giant branch and horizontal branch)
we find, for the Galactic bulge, sigma_l= 0.33 +- 0.03 and sigma_b= 0.25 +-
0.02 arcsec per century. This give sigma_l/sigma_b=1.32 +- 0.16, consistent
both with previous proper motion studies of K giants in the Galactic bulge as
well as with predictions by models of the kinematics of bulge stars.
