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3.4 Absorption Correction

Finally, photometric apparent moduli must be corrected for galactic absorption: µ0 = µ - AB; 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):

Equation 1 (1)


Equation 2 (2)


B1 P Q
N.G.H. -0.188 -0.024 -0.004
S.G.H. -0.204 -0.010 +0.032.

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.