Homogeneous photometry and star counts in the field of 9 Galactic star
  clusters
  We present homogeneous $V,I$ CCD photometry of nine stellar fields in the two
inner quadrants of the Galactic plane. The lines-of-view to most of these
fields aim in the direction of the very inner Galaxy, where the Galactic field
is very dense, and extinction is high and patchy. Our nine fields are,
according to several catalogs, centred on Galactic star clusters, namely
Trumpler 13, Trumpler 20, Lynga 4, Hogg 19, Lynga 12, Trumpler 25, Trumpler 26,
Ruprecht 128, and Trumpler 34. Apart from their coordinates, and in some cases
additional basic data (mainly from the 2MASS archive), their properties are
poorly known. By means of star count techniques and field star decontaminated
Color-Magnitude diagrams, the nature and size of these visual over-densities
has been established; and, when possible, new cluster fundamental parameters
have been derived. To strengthen our findings, we complement our data-set with
JHK$_{s}$ photometry from the 2MASS archive, that we analyze using a suitably
defined Q-parameter. Most clusters are projected towards the Carina-Sagittarium
spiral arm. Because of that, we detect in the Color Magnitude Diagrams of most
of the other fields several distinctive sequences produced by young population
within the arm. All the clusters are of intermediate or old age. The most
interesting cases detected by our study are, perhaps, that of Trumpler 20,
which seems to be much older than previously believed, as indicated by its
prominent -and double- red clump; and that of Hogg 19, a previously overlooked
old open cluster, whose existence in such regions of the Milky Way is puzzling.
