Observers should note that due to a slight mis-alignment
of the Direct Image Mirror (DIM) the row position of a
source imaged with the DIM in, can be several rows different
from the row position of the resulting spectrum (DIM out).

This offset can change after maintenance of the DIM mechanism.

The offset has no adverse affect on spectra and does not affect
positions of sources relative to the slit.

John Rayner 1/11/97