Several possibilities.
Laser pointer. Just because you are surrounded by a couple million hectares of NP doesn't mean someone isn't IN the NP either doing astronomy themselves, or up to something else.
Bugs. I have taken bug trails before in the darkest conditions. You'd be surprised.
Tripod movement. Unless you have an ultra rock steady tripod, even a good mini gust of wind can d this. Or something bumped it, or even a slight ground vibration (heavy enough vehicle) or...
Aliens. Yup, those little green boogers are doing aerobatics in space. Saw you imaging on B Crucis, and thought, let's screw his mind
