3.4 Absorption Correction

Finally, photometric apparent moduli must be corrected for galactic absorption: µ₀ = µ - A_B; the correction was computed through the following equation derived from a new analysis of the Mount Wilson (Hubble's) counts (de Vaucouleurs and Malik 1969):

(1)

where

(2)

and

The value used here for the optical half-thickness of the Galaxy, A₁ = 0.2 mag, applies only to a sample selected by apparent brightness; it agrees well with color-excess data (Holmberg 1958; de Vaucouleurs 1961a) down to the lowest galactic latitudes.