Success! - kind of...

I wanted a clear night without northern lights to get nice, circular star trails with the camera pointing towards the celestial north pole. So of course I got an overcast sky with lots of auroral activity...

But the camera could see enough stars enough time to confirm that this setup does indeed yield completely circular trails!

This is what last night looks like when combining all the images together. It's a busy image with the star trails, aircraft navigation light trails, and of course the northern lights.

I also got a nice-looking timelapse of the aurora while the sky was still mostly clear:

The mount at the nadir isn't too prominent. It almost blends into the dark background in the timelapse video. Still, I wish I could make it less obnoxious...