Testing the COBE/IRAS All-Sky Reddening Map Using the Galactic Globular Clusters

We live in a dusty Universe, and correcting for the dust extinction and reddening affects almost all aspects of the optical astronomy. Recently Schlegel, Finkbeiner & Davis published an all-sky reddening map based on the COBE/DIRBE and IRAS/ISSA infrared sky surveys. Their map is intended to supersede the older Burstein & Heiles reddening estimates. In this paper I test this new reddening map by comparing the reddening values for a sample of 110 $|b|>5\deg$ Galactic globular clusters selected from compilation of Harris. I find a good agreement for globular clusters with galactic latitude $|b|>20\deg$ and fair overall agreement for globular clusters with $20>|b|>5\deg$, but with several significant deviations. I discuss four individual clusters with largest deviations, NGC 6144, Terzan 3, NGC 6355 and IC 1276, in order to investigate the reasons for these large deviations. It seems that the new reddening map overestimates the reddening in some large extinction regions. However, with its high spatial resolution the new reddening map can be used to estimate the relative variation of the reddening on scales $\lesssim 10'$.