CCD STROMGREN PHOTOMETRY OF YOUNG REDDENED CLUSTERS

The capabilities of CCD u upsilon by photometry for the study of redde ned young clusters are investigated. Observations of four fields in th e direction of the clusters Basel 1, Berkeley 86, NGC 6704, and NGC 67 56, with a total of 1665 stars measured in at least the y and b bands, produce new estimates for the clusters parameters. The results are co mpared to those from previously published studies in different photome tric systems showing good agreement in the values of color excess and distance modulus, with the exception of NGC 6756, for which an essenti ally larger distance is found. Furthermore, the ages estimated for thi s cluster, Basel 1, and NGC 6704 are found to be higher than previousl y assumed, in particular for the last one. The presence of red giants as cluster members is suggested in Basel 1, NGC 6704, and NGC 6756. (C ) 1997 American Astronomical Society.