Equatorial and inclined sun dials
In this type of equatorial sundials , the gnomon whitch casts the shadow of the dial or has the following characteristics:
-it is parallel to the axis of the earth,
-it is contained in the plane of the meridian of the place
-it form with the horizontal plane an angle equal to the latitude place
The equatorial sundial is the simplest of all sundials. They can do without mathematical calculations and is universal. the time lines are equally spaced at intervals of 15 ° around the gnomon (24 hours x15º = 360 °.
Sundials inclined by contrast are more difficult to estimate, because their planes are as the name suggests, inclined to the sun and therefore are neither horizontal nor vertical, or polar or equatorial, what they confers a special difficulty to the Gnomonic science.