Archaeoastronomy is a term that refers to the study of how people in the past understood astronomical phenomena and interpreted those phenomena through cultural artifacts (typically the construction of megalithic religious sites). The field of ethnoastronomy is closely tied to field of archaeoastronomy. Ethnoastronomy is the study of how people primarily from non-Western societies interpret astronomical phenomena through their cultural worldview.
Most the cultures that are the focus of archaeoastronomy or ethnoastronomy studies would fall under the Pagan umbrella. Those cultures view/ed natural phenomena including astronomical phenomena as being related to the divine and the spirits. Various astronomical phenomena have been seen as religious significant by Pagan cultures. The rising and setting positions of the sun, moon, and planets are often the main phenomena kept track of, though some stars are also occasionally tracked as well.
The primary phenomenon studied within the field is the concept of alignment. That is when an object, building, or anything else on earth appears to be along an imaginary line between an observer and an astronomical object typically on the horizon.
There are many man-made sites with documented astronomical alignments including:
+Newgrange in County Meath, Ireland
+Chaco Canyon Pueblo site in NM, USA
+Stonehenge in Wiltshire, England
+Temple of Kukulcan, Yucatan, Mexico
+Many sites from the Mississippian culture from throughout the South Eastern, USA
+"Manhattan Henge" is a modern but accidental example
Azimuth is the term for the measurement between the imaginary line (vector) of an observer’s direct forward view and true north. It is measured in degrees. In this system north is 0º, east is 90º, south is 180º, and west is 270º. The graphic below illustrates the azimuth degrees of the cardinal and other directions.
The planets and Earth’s moon have a relatively long orbital and declination cycles. For example, the moon takes 19 years for it to be back in the exact same orbital declination and lunar phase. Tracking and constructing structures for lunar alignments has and does occur in some culture, but is not as common as the tracking and constructing of structure for solar alignments.
When it comes to solar phenomena and alignments, the primary ones are the sunrise and sunsets for the December Solstice, March Equinox, June Solstice, and September Equinox. Various Pagan holidays occur in different traditions around those times. Those holidays often mark the border of seasonal changes. Because of that, solar alignments are also a way of keeping track of what time of the year it is. Equinoxes are when the Earth’s equatorial plane passes through the Sun’s equatorial plane. Equinoxes occur around 20 March and then again around 22 September. During the Solstices Earth’s equatorial plane is at its great declination to the Sun’s equatorial plane. They occur around 21 June and 21 December.
The longitude of a particular location has no effect upon the azimuth degree for sunrises and sunsets. Longitude will only affect the timing of those events. Because of that one only needs to find the azimuth degree for a particular latitude. For places below the Arctic circle and above the Antarctic circle, Equinox sunrises alignments will always be found at the azimuth 90º (or east), and Equinox sunsets will always be found at the azimuth 270º (or west). The azimuth for the sunsets and sunrises for the solstices vary widely by latitude. One can easily find the azimuth of sunrise and sunset for most locations through the website timeanddate.com under the column sunrise/set. Alignments for sunrises and sunsets can be calculated using the free program Google Earth. To do so, one goes to a location and then clicks on the ruler tool. The ruler tool in addition to measuring distance also measures the heading of the line one creates. In this instance, heading and azimuth degree will be synonymous. Using this method one can discover that the sunset on the Equinoxes to an observer standing where the end of Baytree Road in Valdosta, GA meets the campus of Valdosta State University is nearly perfectly aligned with the course of Baytree Road.
The above photo is from the location described during the March Equinox of 2015.
Below is a table with various locations and the azimuth degrees for major solar events for those locations. Locations are arranged north to south. The cities listed are ones near major lines of latitude to help aid in the approximation of azimuth degrees for places between those lines of latitude.
|Latitude||Location||December Solstice Sunrise||December Solstice Sunset||March Equinox Sunrise||March Equinox Sunset||June Solstice Sunrise||June Solstice Sunset||September Solstice Sunrise||September Solstice Sunset|
|90º00N||North Pole||No sunrise||No sunset|
|79º59N||Eureka, Canada||No sunrise||86º||275º||No sunset||86º||275º|
|70º05N||Vadso, Norway||No sunrise||90º||270º||No sunset||90º||270º|
|66º33N||Arctic Circle||116º||186º||90º||270º||No sunset||90º||270º|
|23º26N||Tropic of Cancer||115º||245º||90º||270º||64º||296º||90º||270º|
|10º01N||Alajuela, Costa Rica||114º||246º||90º||270º||66º||296º||90º||270º|
|20º10S||Port Louis, Mauritius||115º||245º||90º||270º||65º||295º||90º||270º|
|23º26S||Tropic of Capricorn||116º||244º||90º||270º||65º||295º||90º||270º|
|25º04S||Adamstown, Pitcairn Islands||116º||244º||90º||270º||64º||296º||90º||270º|
|30º02S||Porto Alegre, Brazil||118º||242º||90º||270º||63º||297º||90º||270º|
|90º00S||South Pole||No sunset||No sunrise|
The graphic below shows the range in sunrise and sunset azimuth variation an observer would see from the VSU end of Baytree Road. The red area on the right shows the sunrise azimuth flux between the Equinoxes and the June Solstice. The red area on the left shows the sunset azimuth flux between the Equinoxes and the June Solstice. The blue area on the right shows the sunrise azimuth flux between the Equinoxes and the December Solstice. The blue area on the left shows the sunset azimuth flux between the Equinoxes and the December Solstice.