Abstract
By employing two different spectroscopic techniques we have mapped out the variable ISM dust extinction endemic to globular cluster M4. We derive an average E(B - V) reddening of 0.33 +/- 0.01 and R = 3.4+/-0.4, both in good agreement with previous studies of M4. For individual stars in the most heavily reddened regions of M4, we find E(B - V) values significantly higher than those inferred by studies of interstellar gas, for heavily reddened regions, the gas measured in column density measurements may not completely trace the dust.
