Polar Dial

A polar dial is a Sundial whose style, parallel with the axis of the poles, is also parallel to the table. This one is thus tilted compared to the horizontal one, of an angle equal to the latitude of the place, and directed perpendicular to meridian of the place. Placed at the pole, the polar dial becomes vertical. At the equator it becomes horizontal.

The time lines all are parallel between them, and their distance $d$ compared to the line of 12:00 on the equinoctial one is given by the relation

$d= \ alpha \ tan H, \,$

with $\ alpha$ the height of the style compared to the table, and $H$ the time angle compared to midday. The distance between the lines of 9:00 and 12:00 like that between the lines of 12:00 and 15:00 are thus equal to the height of the style.

The advantage of the polar dial is that its layout is independent of the latitude of the place: it depends only on the height of the style compared to the table. One can make use of the polar dial as of a calendar while adding to the style a reference mark fixes whose position of the shade will be evaluated compared to the diurnal hyperboles of particular days (equinoxes, solstices…).

See too

External bonds

sundials with polar style

----

Random links:

_de_la_Mordovie