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). The current value, as of 01 July 2000, is 27 rows.
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 x-position of the slit.
LAST UPDATE: February 1, 2010 (format only)