On one my 11-day solo backpacking trips I use to take in the Grand Canyon, I lined my 4x5 camera up with one of the Canyon's "cathedrals" so its point was under the north star. Unfortunately I fell asleep and did not wake up until the sky had started to lighten up.
I focus on a distant street light, and move the camera to check all corners of the gg. This gives me the right depth of field (at f11-16) to get objects like trees in focus, and since the stars appear to be moving, I don't care if they're slightly out of focus. If anything, it increases their 'size'. But it's important to get the film plane perfectly parallel to the lens, otherwise the same star's trail will appear to change in size and intensity across it's travel. Even so, with wide lenses especially (and no center filter), there is a risk of noticeable artifacts unless the North Star is centered in the frame.