Thanks Ryan
As someone that has to set up every imaging night I use the plate solver to figure out orientation. I’ve spent a good portion of this year working on a larger mosaic and it was generated with the orientation at 120°. I knew roughly the orientation of the camera visually but I would use a plate silver to refuel that to within 1.5°. Bit tedious but only takes a minute or two.
90° is the most common angle so an orientation of 90° or 180+90° (depending on the side of meridian you’re on) but you just need to work with what you’ve created your mosaic as.