SIMBAD references

Interstellar extinction is investigated in a 1.5 square degree area at the Galactic equator (l = 146°, b = +2.6°) in Camelopardalis, in the direction of the association Cam OB3. The study is based on photometric classification, interstellar extinction and distance determination of 1300 stars down to 15.5 mag. We find that the interstellar dust in this direction is concentrated mostly between 150 pc and 1 kpc, i.e. in the Orion spiral arm. There is no dust and O-B star concentration at the expected distance of the Perseus arm. An increase of the extinction and of the number of early-type stars is observed at >3.3 kpc. These features may be tracers of the Outer spiral arm. The Cam OB3 association at 4.23 kpc should also be located within this arm.