  Echelle spectra of the double-lined spectroscopic binary HD 204827 were
obtained on five nights, at a resolving power R = 38,000 and with a S/N ratio =
750 near 6000 A in the final, combined spectrum. The stars show E(B-V) = 1.11
and spectral types near O9.5V and B0.5III. A catalog is presented of 380
diffuse interstellar bands (DIBs) measured between 3900 and 8100 A in the
stars' spectrum. The central wavelengths, the widths (FWHM), and the equivalent
widths of nearly all of the bands are tabulated, along with the minimum
uncertainties in the latter. The reliable removal of very weak stellar lines
from the catalog, and of some stellar lines from the less severe blends with
DIBs, is made generally easy by the highly variable radial velocities of both
stars. The principal result of this investigation is that the great majority of
the bands in the catalog are very weak and relatively narrow. Typical
equivalent widths amount to a few mA, and the band widths (FWHM) are most often
near 0.55 A. Therefore, most of these DIBs can be detected only in spectra
obtained at a resolving power and a S/N ratio at least comparable to those used
here. In addition, the anomalous interstellar reddening and the very high value
of the ratio N(C2)/E(B-V) seen toward HD 204827 indicate that the physical
conditions in one or more of the several interstellar clouds seen in this
direction differ significantly from those found toward the prototypical DIB
target HD 183143, for example. Probably primarily for these reasons, 113 of the
380 bands, or 30%, were not detected in four previous, modern surveys of the
DIBs seen in the spectra of stars other than HD 204827. Both the tabulated data
for the DIBs and a plot of our spectrum of HD 204827 are available online at
http://dibdata.org
