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Interstellar extinction in two concentric square areas of the sizes 1.25 × 1.25 deg2 and 0.2 × 0.2 deg2 in the direction of open cluster King 7 is investigated applying two-dimensional photometric classification of stars observed in the Vilnius seven-color photometric system down to V = 15.5 mag (1084 stars) and 19.5 mag (584 stars), respectively. The cluster members (284 stars) are identified applying their coordinates, proper motions, and parallaxes taken from the Gaia EDR3 catalog. New parameters of the cluster (distance, diameter, interstellar extinction, and age) are obtained. Photogeometric distances of stars are taken from Bailer-Jones et al. (2021) based on the Gaia parallaxes from EDR3. Physically the cluster is located at the outer edge of the Perseus spiral arm at d = 2.74 kpc, its diameter is 9.6 pc, the age is 175 ± 25 Myr, the earliest stars are of spectral classes B6–B7. The average interstellar extinction A V = 4.24 mag. From the radial velocities of CO and the Galactic rotation curve we estimate distances to the nearby dust clouds TGU H989 P2 and P3 at 650–670 pc from the Sun.

The open cluster IC 4996 in Cygnus and its vicinity are investigated by applying a two-dimensional photometric classification of stars measured in the Vilnius seven-color photometric system. Cluster members are identified by applying distances based on the Gaia DR2 parallaxes and the point vector diagram of the Gaia DR2 proper motions. For some B-type stars, spectroscopic MK types are also obtained from the Asiago spectra and collected from the literature. New parameters of the cluster are derived. The interstellar extinction $A_V$ covers a wide range of values, from 1.3 to 2.4 mag; the mean value in the central part of the cluster is 1.8 mag. The cluster distance is 1915 $\pm$ 110 pc, and its age is within 8-10 Myr. The cluster exhibits a long sequence from early-B to G stars, where stars cooler than B8 are in the pre-main-sequence stage. The plot of extinction versus distance shows a steep rise of $A_V$ up to 1.6 mag at 700-800 pc, which is probably related to dust clouds at the edge of the Great Cygnus Rift. The next increase in extinction by an additional 0.8 mag at $d$ $\geq$ 1.7 kpc is probably related to the associations Cyg OB1 and Cyg OB3. The cluster IC 4996 does not belong to the Cyg OB1 association, which is located closer to the Sun, at 1682 $\pm$ 116 pc. It seems likely that the cluster and the surrounding O-B stars have a common origin with the nearby association Cyg OB3 since Gaia data show that these stellar groups are located at a similar distance., 7 pages, 5 figures, updated acknowledgements and references for the use of Gaia data

The medium-band Vilnius photometric system with the mean wavelengths at 345 (U), 374 (P), 405 (X), 466 (Y), 516 (Z), 544 (V), and 656 (S) nm for many years was an important tool to determine interstellar reddenings and distances of single stars due to its ability to classify stars of all temperatures in spectral classes and luminosity classes in the presence of different interstellar reddenings. At present, Gaia DR2 presents distances to stars with an unprecedented accuracy at least up to 3 kpc. However, multicolor photometry, which allows the classification of stars as well as the preliminary determination of stellar temperatures, gravities, metallicities and interstellar reddenings, remains an important method for distant stars. Here we present an empirical calibration of the intrinsic color indices of the Vilnius system in terms of physical parameters of stars for dwarf and giant stars of spectral classes F-G-K-M. In any attempted photometric determination of physical parameters of stars it is important to have an extensive and homogeneous sample of spectroscopically determined parameters for stars for which there are also accurate photometric data. As a source catalogue for the Vilnius photometry the latest updated version of the Catalogue of Photoelectric Observations in the Vilnius System was used, which contains compilations from the published photometry for about 11 000 stars. The stars which had both the Gaia DR2 parallaxes and the determinations of stellar parameters from high-dispersion spectra were extracted from this catalogue. The final sample contains more than 1500 stars of spectral classes F-M. The majority of these stars (ca 70%) are not reddened, for others the values of interstellar reddening AV were determined using the regular techniques of photometric classification in the Vilnius system. The absolute magnitudes MV and consequently the luminosity classes were determined using Gaia DR2 parallaxes. We present the analytical expressions for the effective temperature Teff and surface gravity logg and evaluate the errors of solutions for dwarf and giant stars. To test the accuracy of the proposed method, we have compared our results with the stars observed by Gaia and with the stellar parameters available from the large spectroscopic surveys: APOGEE, Gaia-ESO, GALAH, LAMOST, RAVE and SEGUE. The results of comparison contain 5-6 % outliers.The proposed method allows the fast and straightforward evaluation of stellar physical parameters for the stars observed in the Vilnius photometric system. Despite the fact, that the accuracy of determination is significantly lower than in the case of spectroscopic methods, the method described may be useful for distant faint stars, which are still inaccessible for spectroscopic observations.

Interstellar extinction is investigated in a 2°× 2° area containing the dust and molecular clouds LDN 183 (MBM 37) and LDN 169, which are located at RA = 15h 54m, Dec = − 3°. The study is based on a photometric classification in spectral and luminosity classes of 782 stars selected from the catalogs of 1299 stars down to V = 20 mag observed in the Vilnius seven-color system. For control, the MK types for the 18 brightest stars with V between 8.5 and 12.8 mag were determined spectroscopically. For 14 stars, located closer than 200 pc, distances were calculated from trigonometric parallaxes taken from the Gaia Data Release 1. For about 70% of the observed stars, two-dimensional spectral types, interstellar extinctions AV, and distances were determined. Using 57 stars closer than 200 pc, we estimate that the front edge of the clouds begins at 105 ± 8 pc. The extinction layer in the vicinities of the clouds can be about 20 pc thick. In the outer parts of the clouds and between the clouds, the extinction is 0.5–2.0 mag. Behind the Serpens/Libra clouds, the extinction range does not increase; this means that the dust layer at 105 pc is a single extinction source.

The interstellar extinction is investigated in a 1.5 deg2 area in the direction of the open cluster M29 (NGC 6913) in Cygnus, centered at R.A. = 20h 24m, decl. = +38° 30′. The study is based on photometric classification of 1110 stars in spectral and luminosity classes down to V = 19 mag using photometry in the Vilnius seven-color system published in Paper I (Milasius et al. 2013). Additionally, in the same area the extinction is investigated using 1147 red clump giants (RCGs), identified by combining selected two-color diagrams of the 2MASS and Spitzer surveys. The investigated area is divided into three parts with different obscuration and in these directions the extinction versus distance plots up to 5 kpc are presented. In the whole area a steep rise of the extinction is observed at a distance of ∼800 pc; it should be related to dust clouds in the Great Cygnus Rift obscuring the stars behind it by AV = 4.0–4.7 mag. RCGs exhibit much larger extinction values, up to = 1.2–1.3 mag in the more transparent areas and 1.45 mag in the northeastern part of the area and above it, where the dust cloud TGU H466 is located. These values of correspond to AV = 10–12 mag. We do not exclude the possibility that the largest values of the extinction belong not to RCGs but to some contaminating intrinsically red AGB stars penetrated through the applied RCG selection constraints. The extinction in the TGU H466 cloud probably originates in two cloud systems—the Great Cygnus Rift at 800 pc and the Cygnus X complex of dust and molecular clouds at 1.3–1.5 kpc.