1994A&AS..108..581S

Two-dimensional classification of 65 stars up to 3.2kpc based on their seven-color CCD photometry in the Vilnius system has been obtained in a field of 7.3x4.5' size in the direction of the globular cluster M 71. In this paper we have used 43 stars up to 2.0kpc. The photometric classification has been performed by an automated method which uses positions of the program stars in special Q-Q, Q-color index or two color diagrams. Errors of spectral type, M_V and E(B-V) have been determined using the signal-to-noise ratios for each magnitude of a star. The dependence of E(B-V) on distance shows a dispersion which appears to be significantly larger than the observational errors. Assuming that this scattering is mainly caused by the cloudy structure of interstellar dust, a statistical analysis of the data permits to determine the reddening caused by the single cloud and the frequency of clouds. Our mean E(B-V) and the neutral hydrogen column density from the radio measurements give the gas-to-dust ratio in the direction M 71.