Photograph star trails in both hemispheres
Record a timed exposure with known latitude and camera orientation. Compare the trail’s centre, direction and angular motion with the selected sky geometry.
What you need
- Tripod and timed camera exposures
- Clock, coordinates and compass reference
- Dark sky and identifiable stars
Collect the readings
- Choose a celestial-pole field or a star of known declination. Record the latitude, UTC interval, lens and camera direction. Keep the camera stationary; an equatorial tracking mount would remove the effect you intend to measure.
- Take several short exposures over the recorded interval, retaining their original timestamps. Check that foreground objects stay registered so accidental camera movement is visible.
- Enter declination, starting hour angle and total duration in the star-trail calculator. Compare only the predicted above-horizon segment with the photograph.
- For a southern comparison, point to the southern celestial pole rather than assuming Polaris has a southern counterpart at the same brightness. Exchange coordinate and orientation records before comparing clockwise appearance.
Compare the predictions
The celestial pole’s altitude follows the observer’s latitude and hemisphere.
A sidereal rotation changes hour angle about 15° per hour; a near-pole star traces a smaller angular path on the sky.
Image handedness and camera orientation must be held explicit.
Open the related calculation →