Star Trail Simulator
Point the camera, pick the lens, and see the trails before you lose a night finding out.
Sky above
How to read it
The sky turns about the celestial pole, which sits due north (or south) at an altitude equal to your latitude — the point the trails circle. Stars near the pole draw short arcs; stars near the celestial equator draw the longest, 15° per hour of exposure. Wider lenses fit the whole rotation but shrink each arc; longer lenses turn a few stars into long sweeping lines. Each trail is drawn only while the star is inside the frame, so an arc that stops at an edge is a star leaving the picture.
FAQ
- Do I shoot one long exposure or many short ones?
- Many short ones — typically 30 s each, back to back — then stack them. It keeps noise and sky glow under control and a single passing car doesn't ruin the night. The simulator shows the combined result either way.
- Why do the arcs curve the other way at the bottom of the frame?
- Because you're looking past the pole. Trails circle the pole; on the far side of it they curve the opposite way, and along the celestial equator they run nearly straight.
- What settings for a single frame?
- Wide open, ISO 800–3200, 20–30 s. For pin-sharp stars in one frame use the star photography calculator; for trails you want the opposite — let them move.