THE EXTRAGALACTIC DISTANCE SCALE - ZERO POINTS AND GALACTIC EXTINCTION

The zero points of the primary extragalactic distance indicators (Nova e, Cepheids, RR Lyrae and Mira stars), are revised. They differ very L ittle from the zero points adopted originally in the EDS series (ApJ 1 978-79). The evidence for or against different Galactic extinction mod els is reviewed; some tests favor the RC2 model, others the RC3 model (after Burstein and Heiles). An intermediate two-component model is su ggested, with polar reddening E(B - V) similar or equal to 0.02-0.03 a rising near the Galactic plane (z less than or equal to 1 kpc), indica ted by stellar studies and another 0.02-0.03 arising in an extended Ga lactic corona (z less than or equal to 10 kpc), indicated by galaxy an d background studies.