Measured degree of polarization for the HiVIS daytime sky polarization spectra. The telescope was pointed at the zenith (elevation = 90°) as the telescope azimuth was changed between [90, 180, 270 and 360] as a sequence in time. The different symbols show two different spectral orders: 6700 Å as diamonds and 8200 Å as triangles. Different colors represent different telescope azimuths as outlined in the legend. As the sun sets, the Zenith degree of polarization is expected to rise nearly linearly as the solar elevation angle decreases.