  Open clusters are known as excellent tracers of the structure and chemical
evolution of the Galactic disk, however, the accuracy and reliability of open
cluster parameters is poorly known. In recent years, several studies aimed to
present homogeneous open cluster parameter compilations, which are based on
some different approaches and photometric data. These catalogues are excellent
sources to facilitate testing of the actual accuracy of open cluster
parameters. We compare seven cluster parameter compilations statistically and
with an external sample, which comprises the mean results of individual
studies. Furthermore, we selected the objects IC 4651, NGC 2158, NGC 2383, NGC
2489, NGC 2627, NGC 6603, and Trumpler 14, with the main aim to highlight
differences in the fitting solutions. We derived correction terms for each
cluster parameter, using the external calibration sample. Most results by the
compilations are reasonable scaled, but there are trends or constant offsets of
different degree. We also identified one data set, which appears too erroneous
to allow adjustments. After the correction, the mean intrinsic errors amount to
about 0.2 dex for the age, 0.08 mag for the reddening, and 0.35 mag for the
distance modulus. However, there is no study that characterises the cluster
morphologies of all test cases in a correct and consistent manner. Furthermore,
we found that the largest compilations probably include at least 20 percent of
problematic objects, for which the parameters differ significantly. These could
be among others doubtful or unlikely open clusters that do not facilitate an
unambiguous fitting solution.
