  Using observations from the Hubble Space Telescope archive, color-magnitude
diagrams (CMDs) have been constructed for globular cluster 4 in the Fornax dSph
galaxy and its surrounding field. These diagrams extend below the main-sequence
turnoffs and have yielded measurements of the ages of the populations.
  The most prominent features of the CMD of the Fornax field population are a
heavily populated red clump of horizontal branch (HB) stars, a broad red giant
branch (RGB), and a main sequence that spans a large range in luminosity. In
this CMD, there are very few stars at the positions of the HBs of the five
globular clusters in Fornax, which suggests that only a very small fraction of
the field population resembles the clusters in age and chemical composition.
The large span in luminosity of the main-sequence suggests that star formation
began in the field about 12 Gyrs ago and continued to about 0.5 Gyr ago. There
are separate subgiant branches in the CMD, which indicate that the star
formation was not continuous but occurred in bursts. The CMD of cluster 4 has a
steep RGB, from which we estimate [Fe/H] around -2.0. This is considerably
lower than estimates from the integrated light of the cluster, and the origins
of this discrepancy are discussed.
