# Polar sundial

A **polar sundial** is a type of sundial in which the dial contains a parallel line to the earth's axis . If a pole rod is used as a shadow thrower , it is parallel to the dial, its shadow lines are parallel to it and to each other. So they do not intersect at one point, but are arranged like the rungs of a ladder - but with unequal distances between them.

## Polar south clock

With the *polar south clock* , the normal of the dial is in the meridian plane . The marking of the noon shadow is located directly under the pole rod. The remaining hour lines have the distance *c = d · tan (τ)* ( *d* is the distance of the pole rod over the dial, *τ* is the hour angle of the sun). The dial is typically scaled from 7 a.m. to 5 p.m. ( true local time ). The displays for 6 o'clock and 6 o'clock are not possible because the shadow of the pole rod at these moments would theoretically be infinitely long.

## Polar east and west clock

The *(polar) east sundial* (the normal of the wall points to the east: "east wall") or the *(polar) west sundial* (normal points to the west: "west wall") are created with other special positions of the dial . With the east clock, the scaling usually ends at 11 o'clock, with the west clock it starts at 1 p.m. In both cases, the shadow at noon would theoretically be infinitely long. The distance of the hour lines from the line directly under the pole rod is *c = d ÷ tan (τ)* (line under the pole rod for 6 o'clock in the morning or at 6 o'clock in the evening).

The polar east and the polar west sundials are mostly only referred to as *east and west* sundials because they are also special cases of vertical sundials.