Jerky rotation animation

1

I’m trying to recreate the sky with a rotating clip in the shape of an arc. I’ve tried the built-in timer that changes the rotation, I’ve tried the TweenMax class, and I’ve tried hand-building the animation with a motion tween. In all cases, the movement is jerky–smooth for about five frames, then a sudden jerk of motion. What can I do to make this animation smoother? Clip is about 2400px wide, 400px high, with a reg point about 3000px away that it rotates around.