Thanks for series of tips..!
First, yes, it is a genuinely new one (so includes all latest bells and whistles)
You will see I noted to Andy that the kind of spectrum I was getting was similar to the one he posted (bimodal cross section) so I’m not sure about the focus thing? I focus the collimator (terminology? i.e. the assembly behind the small door on the side) against the FWHM of the calibration lines.
The bimodal feature appears to come and go as I move the main mirror about its fulcrum. However, I see you recommend placing it about 1/3 way *up* (with red on right). I have it about 1/3 way *down* so maybe I’ll try swinging across the field of view (and taking some cross-sectional integrated flux measurements as I do so).