SIMBAD references

Two-dimensional classification of field stars based on their seven-color CCD photometry in the Vilnius system has been obtained in two small fields on either side of the globular cluster M 56. The purely photometric classification has been performed using an automated software package (ASCAR). Mean values of E(B-V) for each field respectively have been determined from foreground stars. In both fields the dependence of E(B-V) on distance shows a dispersion which seems to be larger than the observational errors. Assuming that this scattering is mainly caused by the cloudy structure of interstellar dust, an attempt has been made to determine statistically the reddening caused by a single cloud and the frequency of clouds. The mean values of E(B-V) in each field respectively and, by comparison with the radio measurements, the gas-to-dust ratio in the direction of M 56 have been determined. The present analysis confirms the possibility of a variation of reddening across the cluster face.