  We present a simple approach for obtaining robust values of astrophysical
parameters from the observed colour-magnitude diagrams (CMDs) of star clusters.
The basic inputs are the Hess diagram built with the photometric measurements
of a star cluster and a set of isochrones covering wide ranges of age and
metallicity. In short, each isochrone is shifted in apparent distance modulus
and colour excess until it crosses over the maximum possible Hess density.
Repeating this step for all available isochrones leads to the construction of
the solution map, in which the optimum values of age and metallicity - as well
as foreground/background reddening and distance from the Sun - can be searched
for. Controlled tests with simulated CMDs show that the approach is efficient
in recovering the input values. We apply the approach to the open clusters
M\,67, NGC\,6791, and NGC\,2635, which are characterised by different ages,
metallicities and distances from the Sun.
