Polar Alignment Calculator — Equatorial Mount Setup

The celestial pole altitude equals your geographic latitude, so you set the mount altitude to your latitude. In the northern hemisphere, Polaris sits approximately 0.65° from the true North Celestial Pole (as of 2026), which is why pointing at Polaris alone is not precise enough.

Pole altitude = observer latitude

Star trailing from a polar-alignment error is driven by the sidereal rate (≈15 arcsec/s) acting on the misalignment angle expressed in radians. A 1-arcminute alignment error causes a worst-case declination drift of about 0.262 arcsec per minute of time (≈0.0044 arcsec per second) — measured for a star on the celestial equator near the meridian. The drift is largest at the celestial equator and falls to zero at the pole.

Trail (arcsec) = error (arcmin) × 0.00437 × exposure (s)

The alignment tolerance is the largest error that keeps this trail within an acceptable budget (here ≈2 arcsec, about one pixel for a typical deep-sky rig) over your chosen exposure. Longer exposures therefore demand tighter alignment.