Different Types of Sundials

There are many types of sundials but they can be grouped into three main classes:

1. Those having a gnomon parallel to the Earth's axis, and around which the Sun and all celestial bodies appear to move at a rate of 15º per hour. The earth turns 360º in about 24 hours, therefore the sun's apparent position moves 360/24 = 15º each hour.
2. Those that depend on the altitude of the Sun above the horizon. These dials are known as altitude dials.
3. Those that depend on the Sun's azimuth. They are known as azimuth dials.

These three classes of sundials can again be grouped into 2 different types:

1. Pole - style
2. Nodal