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). The distance between PY or PX will be the Polar distance of the body. NP=ZQ=Latitude of observer NY and NX will be the True altitude of body at that instant. Polar distance (PD) = 90° ± δ Polar distances are expressed in
degrees and cannot exceed 180° in magnitude. An object on the celestial equator has a PD of 90°. 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. ==References==