Stars move 15 arcseconds per second of time at the celestial equator, less toward the poles. This calculator converts your exposure into a trail length in pixels — useful both for avoiding trails (sharp stars) and for planning deliberate star-trail images.
Pixel pitch is listed on every camera page in our database.
How it works
Trail (px) = 15.04″/s × t × cos δ ÷ (206.265 × p / f).
FAQ
Why do stars near Polaris trail less?
They trace small circles around the celestial pole, so they move fewer arcseconds per second.
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