It was a really clear night on Saturday for another startrail test. While I probably could have done without the lens flare, I really liked how clear the umbrella and tree foreground turned out.
In a given 24-hour cycle, the stars will rotate around the North Star a full 360 degrees. That is, 15 degrees every hour. I suppose you could leave your shutter open for a full hour with the bulb, but I’m guessing you’ll have let so much light in, you’ll be left with an entirely white exposure.
Instead, I find the easiest thing to do is a 30 second exposure with the intervalometer set to 35 seconds. Then the aforementioned ImageMagick script or Photoshop action script will do the rest.
Below is essentially a composite 2-hour exposure:
35s intervals x 200 frames @ 10fps (about 2 hours)