The slicer output must lie horizontal to maintain maximum resolution through the spectrograph optics. The required slit angle is currently SA 2160 (ADU), but can be checked as follows. A spirit level can be used to mark the horizontal across the back of the slit/slicer carriage, and a white straight-edge ( e.g. the edge of a sheet of paper) taped level with this. The slicer can be illuminated with the quartz lamp and its output face viewed from the collimator with the UKST 3 inch Questar. The slit angle SA can then be changed to make the two parallel.
It can also be checked using an eyepiece at the UHRF focus, provided the detector is not yet mounted. In this case use the eyepiece mounting plate with the eyepiece from the binocular in the chart room. Configure the spectrograph for the laser. You will have to remove the diffuser disk in front of the laser and possibly the diffuser from the pupil simulator to get enough light to the eyepiece. You should be able to determine the rotation required to make the output horizontal.