The spirit level only levels the camera. It does not level the horizon. Most of the time when doing star trail, I am tilting the camera up to capture more of the sky. The horizon may not run parallel to the ground.
ok. I know there may not be an easy way. Can those who shoot in the night share with me some of the techniques they use to see "in the dark". Right now, I am shooting a 2 min ISO3200 exposure for me to see and then do the actual shoot. But this is very labourious to do in the dark. Do a test shot, adjust in the dark, then do another test shot, adjust some more and so on...