Star Trail Calculator
Estimate the total capture time, apparent sky sweep and horizontal framing coverage for a star-trail sequence.
A QUICK WALKTHROUGH
How to use this tool
- Enter the exposure and interval used by your intervalometer.
- Set the number of frames and the camera’s focal length and sensor width.
- Use the result to judge sequence duration and whether the sweep will span the frame.
Planning approximation
The displayed sweep describes angular sky motion during the planned sequence. Stacking separate frames can show gaps if the interval is long or if frames are interrupted.
Camera inputs
Focal length and sensor width are used only for a horizontal field-of-view estimate. Use the actual sensor dimension across the frame; crop modes change the effective field of view.
GOOD TO KNOW
Common questions
Does this predict the exact star trail shape?
No. It estimates angular motion and horizontal framing coverage. Exact arcs depend on the camera direction, latitude and star declination.
Does it choose exposure settings?
No. Exposure, interval and frame count are your camera or intervalometer settings.
Are my values uploaded?
No. The calculation runs in your browser.