One Star to Tag Them All (OSTTA): I. Radial velocities and chemical
  abundances for 20 poorly studied open clusters
  Context: Open clusters are ideal laboratories to investigate a variety of
astrophysical topics, from the properties of the Galactic disc to stellar
evolution models. For this purpose, we need to know their chemical composition
in detail. Unfortunately, the number of systems with chemical abundances
determined from high resolution spectroscopy remains small. Aims: Our aim is to
increase the number of open clusters with radial velocities and chemical
abundances determined from high resolution spectroscopy by sampling a few stars
in clusters not studied previously. Methods: We obtained high resolution
spectra with the FIES spectrograph at NOT for 41 stars belonging to 20 open
clusters. These stars have high astrometric membership probabilities,
determined from the Gaia second data release. Results: We derived radial
velocities for all the observed stars, which were used to confirm their
membership to the corresponding clusters. For Gulliver\,37 we cannot be sure
the observed star is a real member. We derived atmospheric parameters for the
32 stars considered real cluster members. We discarded five stars because they
have very low gravity or atmospheric parameters were not properly constrained
due to low signal-to-noise ratio spectra. Therefore, detailed chemical
abundances were determined for 28 stars belonging to 17 clusters. For most of
them, this is the first chemical analysis available in the literature. Finally,
we compared the clusters in our sample to a large population of well studied
clusters. The studied systems follow the trends, both chemical and kinematical,
described by the majority of open clusters. Worth noticing that the three most
metal-poor studied clusters (NGC\,1027, NGC\,1750 and Trumpler 2) are enhanced
in Si but not in the other alpha-elements studied (Mg, Ca and Ti).
