Comparison of the Dawn albedo map of (4) Vesta (V. Reddy et al. 2012) with POLISH2 linear polarimetry (Figure 3). As expected from the Umov effect, linear polarization increases as the dark Olbers Regio comes into view (longitude ∼300°) and decreases over the bright regions. Subobserver longitudes for POLISH2 observations are obtained from the JPL Horizons database, and the dashed red line indicates the mean subobserver latitude of −30﹩\mathop{.}\limits^{\unicode{x000b0}}﹩26 ± 0﹩\mathop{.}\limits^{\unicode{x000b0}}﹩31 during POLISH2 observations. The Dawn albedo map is modified from V. Reddy et al. (2012) with permission from AAAS.