What is an Analemmatic Sundial?

The Sundial at NWF State College is called an analemmatic sundial. The word analemma is an ancient one, with various meanings. But as it is used today the analemma refers to the pattern made by the Sun in the sky, as seen over a year's time (Figure 6). In other words, if you were to take a photograph of the Sun, at the same place and same time of day, every two weeks or so, and then combine all of those photos into one image, you would see that the Sun follows a figure-8 path across the sky throughout the year. The reason for this path has to do with the changing position of the Earth relative to the Sun during its annual orbit.

Analemmatic sundials are a type of horizontal dial* that use a vertical gnomon, which is adjusted on the dial depending on the time of year (since the Sun changes its declination in the sky throughout the year - lower in the winter, higher in the summer). The oldest known analemmatic dial is still operational and is located at the Church of Brou, in Bourg-en-Bresse, France (about 230 miles southeast of Paris). This dial is reportedly as old as the church itself, which dates to 1506.

* Horizontal dials are oriented parallel to the ground, rather than parallel to the spin axis of the Earth (as in the majority of dials).