  Many open clusters listed in modern catalogues were initially reported by
visual astronomers as apparent overdensities of bright stars. As observational
techniques and analysis methods continue to improve, some of them have been
shown to be chance alignments of stars and not true clusters. Recent
publications have provided membership lists for over a thousand clusters,
however, many nearby objects listed in the literature have so far evaded
detection. We aim to update the Gaia DR2 cluster census by performing
membership determinations for known clusters that had been missed by previous
studies and for recently-discovered clusters. We investigate a sub-set of
non-detected clusters that, according to their literature parameters, should be
easily visible in Gaia. Confirming or disproving the existence of old,
inner-disc, high-altitude clusters is especially important as their survival or
disruption is linked to the dynamical processes that drive the evolution of the
Milky Way. We employed the Gaia DR2 catalogue and a membership assignment
procedure, as well as visual inspections of spatial, proper motion, and
parallax distributions. We used membership lists provided by other authors when
available. We derived membership lists for 150 objects, including ten that were
already known prior to Gaia. We compiled a final list of members for 1481
clusters. Among the objects that we are still unable to identify with the Gaia
data, we argue that many (mostly putatively old, relatively nearby,
high-altitude objects) are not true clusters. At present, the only confirmed
cluster located further than 500pc away from the Galactic plane within the
Solar circle is NGC 6791. It is likely that the objects discussed in this study
only represent a fraction of the non-physical groupings erroneously listed in
the catalogues as genuine open clusters and that those lists need further
cleaning.
