  The Doppler shifts of optical emission lines which have been scattered by
surrounding dust and electrons can provide useful information about the
kinematics, geometry and physical conditions of astrophysical flows. In
principle, the scatterers can provide views of the line-emitting gas from
different directions, allowing the 3-d velocity field of the emitting gas to be
determined and revealing sources which are hidden from direct view.
Unfortunately, as in a Hall of Mirrors, the resultant multiple images can be
confusing and hard to interpret. In general, the scattering geometry will be
unknown, which makes it difficult to disentangle the effect of the motion of
the scatterers from that of the motion of the emitting source. In this
situation, spectropolarimetric observations can be a great help, since the
scattered light will be partially polarised to a degree dependent on the angle
of scattering and on the details of the scattering process. Analysis of the
polarisation profiles of the scattered emission lines can then determine the
relative orientation and velocity of the source and the scatterers. Such
techniques are applied to the upstream scattered emission lines in the HH 1
jet, where it is shown that spectropolarimetric measurements would allow an
independent determination of the bowshock velocity with respect to the upstream
matter, which would test ``multiple outburst'' models of the jet.
