A star tracker is a small motorized mount that rotates your camera at the same speed the sky turns. It lets you expose for minutes instead of seconds — at low ISO, with far less noise.
Why use one
Without tracking, the NPF rule limits a 24 mm lens to roughly 10 seconds. With a tracker you can shoot 1–4 minutes at ISO 400–800, revealing faint dust lanes and color that high-ISO single frames can't.
Polar alignment
The tracker's axis must point at the celestial pole — near Polaris in the Northern Hemisphere.
- Level the tripod and set the wedge to your latitude.
- Look through the polar scope and place Polaris at the position shown by a polar-alignment app for the current time.
- Accuracy needed depends on focal length and exposure: wide lenses forgive small errors; 135 mm and longer need careful alignment.
Exposure plan
| Focal length | Typical tracked exposure |
|---|---|
| 14–24 mm | 2–4 min |
| 35–50 mm | 1–2 min |
| 85–135 mm | 30–90 s |
Shoot several sub-exposures and stack them; the astro stacking calculator shows the noise improvement and total integration time.
The foreground problem
Tracking blurs the landscape. Solutions:
- Shoot the sky tracked and the foreground untracked (tracker off) from the same tripod position, then blend.
- Shoot the foreground at blue hour for clean detail.
Common mistakes
- Unbalanced load — counterweight heavy lenses.
- Touching the camera: use an intervalometer.
- Wind: lower the tripod and hang a bag from it.
- Dew: use a lens heater.
Check your image scale and field of view with the image scale calculator.
About 1 min read · Updated 2026-10-20