Last night I was able to capture 8.9hrs of star movement before the batteries gave out. I used 18mm lens, ISO 800, f/3.5, 13" exposure with 45" interval. No telescope was used, just the camera. The resulting 24fps video is about 30sec long. I think the footage isn't quite as smooth as when I used a 30" interval. Some clouds enter the frame towards the end and I like how they turned out.
This is one of those things I just wanted to try, to see if I could do it. I used to think it was too difficult to take pictures of the stars, but now I know I can do it. My goals for star timelapse are (1) Milky Way and (2) a meteor shower. I'll have to wait until next winter for optimal Milky Way viewing and active meteor showers, but at least I know what to do when the time comes.