Spectroscopy of diffuse light in dust clouds. Scattered light and the
  solar neighbourhood radiation field
  The optical surface brightness of dark nebulae is mainly due to scattering of
integrated starlight by classical dust grains. It contains information on the
impinging interstellar radiation field, cloud structure, and grain scattering
properties. We have obtained spectra of the scattered light from 3500 to 9000
Angstrom in two globules, the Thumbprint Nebula and DC303.8-14.2.
  We use observations of the scattered light to study the impinging integrated
starlight spectrum as well as the scattered H-alpha and other line emissions
from all over the sky. We search also for the presence of other than scattered
light in the two globules.
  We obtained long-slit spectra encompassing the whole globule plus adjacent
sky in a one-slit setting, thus enabling efficient elimination of airglow and
other foreground sky components. We calculated synthetic integrated starlight
spectra for the solar neighbourhood using HIPPARCOS-based stellar distributions
and the spectral library of Pickles.
  Spectra are presented separately for the bright rims and dark cores of the
globules. The continuum spectral energy distributions and absorption line
spectra can be well modelled with the synthetic integrated starlight spectra.
Emission lines of H-alpha + NII, H-beta, and SII are detected and are
interpreted in terms of scattered light plus an in situ warm ionized medium
component behind the globules. We detected an excess of emission over the
wavelength range 5200-8000 Angstrom in DC303.8-14.2 but the nature of this
emission remains open.
