The Zero Point of Extinction toward Baade's Window from K Giants

We measure the zero point of the Stanek extinction map by comparing the observed ( V - K ) colors of 206 K giant stars with their intrinsic ( V - K ) 0 colors as derived from their Hβ indices. We find that the zero point of the Stanek map should be changed by Δ A V = -0.10 ± 0.06 mag, obtaining as a bonus a threefold reduction of the previous statistical error. The most direct way to test for systematic errors in this determination would be to conduct a parallel measurement based on the ( V - K ) colors of type ab RR Lyrae stars.