Symbols & Features on the NWF State College Sundial

There are several artistic and scientific symbols on the NWFSC Interactive Analemmatic Sundial. The hour marks of the elliptical dial are represented by Roman numerals, representing 5:00 AM (V on the left) to 7:00 PM (VII on the right). Between each numeral are half-hour marks (wedge-shaped). Ante Meridiem (a.m.) and Post Meridiem (p.m.) mark the morning and evening hours, respectively. Also below the hour marks, starting at VIII on the left and extending to V on the right, are the astronomical symbols for the 7 "wanderers" for which the days of the week are named. "Wanderers" were what the ancients called the Sun, Moon, and 5 visible (to the naked eye) planets. Unlike the stars, the wanderers move across the sky independent of the pattern and motion of the stars. The origin of this system is a bit complex, but basically each day was named for one of the wanderers.

Symbols of planets

On the left side of the dial is the prominent compass rose, which shows the directions of North, South, East, and West (it is critical that the sundial be perfectly oriented to the North Pole). On the right is the beautifulface of the Sun, rising in the East. The bear represents the Great Bear constellation of the northern sky, Ursa major. The Great Bear is one of the most ancient of constellations, and may have been inspired by the lore of prehistoric peoples. Within Ursa major proper is a sub-constellation (or asterism) well-known to all as the Big Dipper, which is in the back and tail of the bear. The two stars at the end of the "cup" of the dipper are called pointer stars because if you imagine a line and arrow formed by them, they point towards Polaris, also known as the North Star, which is represented just below the XII by a solar cell light so that it may be seen at night.

In middle of the dial is the long, rectangular, scale of dates, on which the observer stands to casts a shadow on the dial. The months of the year are all recognized by a 3-letter abbreviation. Within the month boxes are peculiar symbols that represent the constellations of the zodiac. The zodiac refers to 12 ancient constellations that lie within an 18-wide band of sky called the ecliptic. The ecliptic is the path that the Sun, Moon, and planets follow in their courses across the sky. Technically, the ecliptic is the plane of the solar system. The date associated with each constellation of the zodiac corresponds to the day in which the Sun begins to rise within that constellation in the eastern sky. Each zodiacal constellation occupies 30 of sky.

Zodical Constellation Dates

(Latin) (English) Sun Enters Sign Season
Aries Ram Mar. 20th spring
Taurus Bull Apr. 20th spring
Gemini Twins May 21st spring
Cancer Crab June 21st summer
Leo Lion July 23rd summer
Virgo Virgin Aug. 23rd summer
Libra Scales Sept. 23rd autumn
Scorpio Scorpion Oct. 23rd autumn
Sagittarius Archer Nov. 22nd autumn
Capricornus Goat Dec. 21st winter
Aquarius Water bearer Jan. 20th winter
Pisces Fishes Feb. 18th winter

 

On the top and bottom of the scale of dates are the letters, Sol, which stand for solstice. On the summer solstice (on or near June 21st), the Sun is directly over the Tropic of Cancer (23.5 North latitude), marking the longest day of the year and the beginning of summer in the Northern Hemisphere. On the winter solstice (on or near December 22nd), the Sun is directly over the Tropic of Capricorn (23.5 South latitude), marking shortest day of the year and the beginning of winter in the Northern Hemisphere.

At the middle, right and left of the scale of dates are the letters, EQ, which stand for equinox. On the fall equiniox (on or near September 23rd), the Sun is directly over the Equator, marking equal lengths of daylight and darkness on that day, and the beginning of autumn. On the spring (or, vernal) equiniox (on or near March 21st), the Sun is also directly over the Equator, marking equal lengths of daylight and darkness on that day, and the beginning of spring. Were it not for the tilt of the Earth on its spin axis (presently tilted at 23.5), there would essentially be only one season throughout the year (like spring or fall). Also on the scale of dates is the figure-8 pattern of the analemma (see discussion under "What is an Analemmaic Sundial?"). An analemma pattern can be used as part of an analemmatic sundial to correct for the equation of time (but it gets very complicated!). The analemma on the NWFSC dial is strictly artistic.