Star trails show Earth's rotation: stars draw arcs as the sky turns about 15° per hour. One long exposure works, but stacking many short frames gives cleaner, more flexible results.
Choose the trail shape
- Point north (toward Polaris) for concentric circles.
- Point east or west for diagonal streaks rising or setting.
- Point south for gentle arcs curving in opposite directions above and below the celestial equator.
How long to shoot
Trail length grows with time: one hour gives 15° arcs; four hours give 60°. Plan the session with the star trail calculator, and see how long trails are in pixels for one frame with the star trail length calculator.
Settings for stacking
- 20–30 s exposures at ISO 400–1600, f/2.8–f/5.6.
- Interval shooting with ≤1 second gaps — longer gaps create dotted trails.
- Long exposure noise reduction off.
- Manual focus, manual white balance, RAW + JPEG (JPEGs make stacking quick).
Stacking
Combine frames with lighten blending: each pixel keeps its brightest value across the sequence. Our in-browser star trail stacker does this without uploading anything; it also offers a "comet" fade for tapered trails. Desktop options include StarStaX and Sequator.
Tips
- A moon at 20–40% lights the foreground nicely without washing out trails.
- Planes and satellites leave lines — remove them from individual frames before stacking.
- Bring two batteries or a USB power source; sessions run for hours.
- The same frames can become a time-lapse — see the time-lapse calculator.
About 1 min read · Updated 2026-10-20