We present CCD photometry in the Johnson UBV and Kron-Cousins I systems down to V~22.0 for the open clusters NGC 2311, Trumpler 6, NGC 2432 and BH 54 and their surrounding fields. Trumpler 6 and BH 54 have never been studied before and so we provide, for the first time, estimates of their fundamental parameters. We obtained colour-magnitude diagrams (CMDs) and colour-colour diagrams cleaned from field star contamination by statistically subtracting stars in terms of spatial density, magnitude and colour distributions. Cluster angular radii were estimated from star counts in appropriate-sized boxes distributed throughout the entire observed fields. Using the cleaned CMDs and colour-colour diagrams, we applied sound photometric membership criteria to discriminate cluster members from interloper field stars. The interstellar extinction across the cluster fields derived from the 100-{mu}m dust emission full-sky maps can be considered uniform within the quoted uncertainties. The E(B-V) and E(V-I) colour excesses and the apparent distance moduli of the clusters were estimated from the fit of the zero-age main-sequence to the colour-colour diagrams and CMDs, respectively. Cluster ages were determined from the comparison of the four clusters' CMDs with solar metallicity theoretical isochrones of the Geneva group. All the clusters were found to be moderately young objects, their ages ranging between 60 and 250Myr.
New photometric material is presented for six outer disc supposedly old, Galactic star clusters: Berkeley 76, Haffner 4, Ruprecht 10, Haffner 7, Haffner 11 and Haffner 15, which are projected against the rich and complex Canis Major overdensity at 225{deg}<=l<=248{deg}, -7{deg}b<=-2{deg}. This CCD data set, in the UBVI passbands, is used to derive their fundamental parameters, in particular age and distance. Four of the program clusters turn out to be older than 1Gyr. This fact makes them ideal targets for future spectroscopic campaigns aiming at deriving their metal abundances. This, in turn, contributes to increase the number of well-studied outer disc old open clusters. Only Haffner 15, previously considered an old cluster, is found to be a young, significantly reddened cluster, member of the Perseus arm in the third Galactic quadrant. As for Haffner 4, we suggest an age of about half a Gyr. The most interesting result we found is that Berkeley 76 is probably located at more than 17kpc from the Galactic centre, and therefore is among the most peripherical old open clusters so far detected. Besides, for Ruprecht 10 and Haffner 7, which were never studied before, we propose ages larger than 1Gyr. All the old clusters of this sample are scarcely populated and show evidence of tidal interaction with the Milky Way, and are therefore most probably in advanced stages of dynamical dissolution.
We have obtained CCD UBVI_KC_ photometry down to V~21.0 for the open clusters Berkeley 26, Czernik 27, Melotte 72, NGC 2479 and BH 37. The latter has never been studied before. Cluster stellar density profiles were obtained from star counts in appropriate-sized boxes distributed throughout the entire observed fields. Based on different measured indices, we estimate the ages of Berkeley 26, Melotte 72 and NGC 2479. On the other hand, we indicate possible solutions for the cluster fundamental parameters by matching theoretical isochrones which reasonably reproduce the main cluster features in their colour-magnitude diagrams. In the case of NGC 2479, the cluster E(BV) and E(VI) colour excesses and apparent distance modulus were estimated from the fit of the zero-age main sequence to the colour-colour and colour-magnitude diagrams, respectively.
We present the results of the photometric CCD search for B-type pulsators in the central region of Chi Persei (NGC 884) open cluster. In addition to the two newly-discovered Beta Cephei stars we found 11 other variables in the observed field. The photometric data for them are given in the file 'bmag' and 'vmag' for B and V-filter data, respectively. In addition, we present the new UBV magnitudes for stars in the observed field. This is Table 4 of the paper, available only in electronic form.
CCD photometry on the UBV and Washington systems, is presented for Be32, a so far unstudied rich open cluster located in the Galactic anticentre. Morphology of cluster and colour-magnitude diagram indicates that it is an old object with age close to ages of NGC 188 and NGC 2243 (about 6Gyr on the scale of VandenBerg isochrones). The cluster reddening is E(B-V)=0.16 and the estimated metallicity is [Fe/H]=-0.37+/-0.05. The apparent distance modulus is between 12.8 and 13.1.
The table 1 lists photoelectric UBV measures for 78 stars in the open cluster NGC 6025. Distance and age estimates derived are 760pc and 100Myr. The brightest star, HD 143448, is a known emission star and is very probably a member of the cluster. Accurate positions and identifications of the stars were added by B. Skiff (Lowell Observatory) in November 2009.
We present UBV photoelectric observations of 345 stars in the field of the southern open cluster NGC 2539. The analysis of these data allows to determine that 169 stars are probable members of the cluster main sequence, while 23 are possible members.
The discovery of several clusters of red supergiants towards l=24{deg}-30{deg} has triggered interest in this area of the Galactic plane, where lines of sight are very complex and previous explorations of the stellar content were very preliminary. We attempt to characterise the stellar population associated with the HII region RCW 173 (=Sh2-60), located at l=25.3{deg}, as previous studies have suggested that this population could be beyond the Sagittarius arm.
Photoelectric UBV photometry and star counts are presented for stars in the previously unstudied open cluster Ruprecht 91, supplemented by observations for stars in adjacent regions surrounding the Cepheids SX Car and VY Car, including new observations for the latter. Ruprecht 91 is typical of groups associated with Cepheids, with an evolutionary age of ~8x10^7^yr, but it is only 980+/-8pc distant, much closer than the Cepheids.
Three-colour photographic photometry of the young open cluster NGC 7510 based upon UBV observations made with the 122cm and 182cm Asiago reflectors is presented here. A mean colour excess E(B-V)=1.12, a distance of 3.09kpc could be achieved for this cluster and 31 stars could be identified as photometric physical members. An age of 10^7^years has been derived by comparison with standard isochrones. The discrepancy between the photometric and spectroscopic distances obtained for some stars is discussed and comparisons with recent investigations of the same object are also given.