Polar distance (astronomy)

Polar distance in celestial navigation is the angle between the pole and the Position of body on its Declination.

Referring to diagram: P- Pole , WQE- Equator , Z - Zenith of observer , Y- Lower meridian passage of body X- Upper meridian passage of body Here body will be on declination circle ( XY).

NP=ZQ=Latitude of observer NY and NX will be the True altitude of body at that instant.

Polar distance is affected by the precession of the equinoxes.

If the polar distance of the Sun is equal to the observer's latitude, the shadow path of a gnomon's tip on a sundial will be a parabola; at higher latitudes it will be an ellipse and lower, a hyperbola.