  We present a spectrum of the diffuse Galactic light (DGL) between 3700 and
10,000 A, obtained by correlating optical sky intensity with far-infrared dust
emission. We use nearly 250,000 blank-sky spectra from BOSS/SDSS-III together
with IRIS-reprocessed maps from the IRAS satellite. The larger sample size
compared to SDSS-II results in a factor-of-two increase in signal to noise. We
combine these data sets with a model for the optical/far-infrared correlation
that accounts for self-absorption by dust. The spectral features of the DGL
agree remarkably well with features present in stellar spectra. There is
evidence for a difference in the DGL continuum between the regions covered by
BOSS in the northern and southern Galactic hemisphere. We interpret the
difference at red wavelengths as the result of a difference in stellar
populations, with mainly old stars in both regions but a higher fraction of
young stars in the south. There is also a broad excess in the southern DGL
spectrum over the prediction of a simple radiative transfer model, without a
clear counterpart in the north. We interpret this excess, centered at ~6500 A,
as evidence for luminescence in the form of extended red emission (ERE). The
observed strength of the 4000 A break indicates that at most ~7% of the
dust-correlated light at 4000 A can be due to blue luminescence. Our DGL
spectrum provides constraints on dust scattering and luminescence independent
of measurements of extinction.
