Studies of A and F stars in the region of the North galactic Pole- V. Interstellar reddening and the uvbybeta intrinsic colour calibration.

A reddening map for the North Galactic Pole region based on uvbyβ photometry of ∼1000 stars with b > 75° is presented. The only significant amount of reddening occurs over about half the field and within the first 100 pc; there is an additional small H I cloud with associated dust at about 120 pc. Otherwise much of the volume seems to be essentially free of interstellar absorption at least out to 1 kpc.

The large amount of data is used, in part, to define for the first time the intrinsic colour and absolute magnitude calibration for uvbyβ photometry of stars in the range -0.01 < (b-y) < 0.06 (B9-A2) as well as to suggest two minor modifications to Crawford's calibrations of this photometric system.