Strange rotation angle in telescope simulator


I’ve used the scope simulator a lot in the past, for putting together mosaics. It’s always worked fine.

Tonight I was using it for a two-pane mosaic of M45. The rotation said 104.4 degrees. However, when I looked at the preview from my camera, it was quite a way out from what I expected. I noticed the FOV angle said East, so on a hunch, wondered if this translated to 75.6 degrees. On rotating my camera to that angle, it was as per the Telescopius preview.

So, I don’t understand why the scope simulator gave me a different angle from that which actually worked. I’ve looked and can’t find a way to make the simulator give a FOV angle West, in case that would change things.

Any ideas?