Determining the distance to the open cluster M29 ( NGC 6913 ) has proven difficult , with distances determined by various authors differing by a factor of two or more .
To solve this problem , we have initiated a new photometric investigation of the cluster in the Vilnius seven-color photometric system supplementing it with available data in the BV and JHK _ { s } photometric systems , and spectra of the nine brightest stars of spectral classes O and B. Photometric spectral classes and luminosities of 260 stars in a 15 \arcmin \times 15 \arcmin area down to V = 19 mag are used to investigate the interstellar extinction run with distance and to estimate the distance of the Great Cygnus Rift , \sim 800 pc .
The interstellar reddening law in the optical and near-infrared regions is found to be close to normal , with the ratio of extinction to color excess R _ { BV } = 2.87 .
The extinction A _ { V } of cluster members is between 2.5 to 3.8 mag , with a mean value of 2.97 mag or E _ { B - V } = 1.03 .
The average distance of eight stars of spectral types O9–B2 is 1.54 \pm 0.15 kpc .
Two stars from the seven brightest ones are field stars : HDE 229238 is a background B0.5 supergiant and HD 194378 is a foreground F star .
In the intrinsic color-magnitude diagram , seven fainter stars of spectral classes B3–B8 are identified as possible members of the cluster .
The 15 selected members of the cluster of spectral classes O9–B8 plotted on the \log L / L _ { \odot } vs . \log T _ { eff } diagram , together with the isochrones from the Padova database , give the age of the cluster as 5 \pm 1 Myr .