Article of the month March

Halazûn

Artikel of the month for November 2006 described the Hâfir, a horizontal sundial from the Arab world.
Here we show the Halazûn, a variation on the theme.


The difference with the Hâfir is in the date scale.
The Hâfir has a circular scale according to the signs of Zodiac, with each sign containing 30 degrees of the ecliptic. Together, they occupy the circumference precisely once.
In the Halazûn, each sign comprises 60 degrees, and the date scale is divided in two separate parts, one each for the lengthening and shortening days.
This is possible because the sun passes through each declination twice each year, and the points of the hour lines are equal on corresponding days.
An advantage is that the date scale is now twice as long.

On the Halazûn, too, Islamic prayer lines frequently occur.
For clarity, the figure below shows them separately.