Full moon extreme positions, lunar standstills and the metonic cycle at Cañada de la Virgen archaeological site

Abstract

The purpose of this work is to show the extreme positions of the full moons of June, seen from the main entrance into the enclosed patio of Complex A at the archaeological site Cañada de la Virgen. These positions are discussed in terms of the cycles known as major and minor lunar standstills, as well as the metonic cycle.
Given the publication guidelines, an enormous effort of synthesis had to be made when dealing with the high number of astronomical events and dates that have been worked through the Permanent Program of Celestial Observations at Cañada de la Virgen. For the same reason, I had to limit possible comparative examples that would serve to justify the dates or “date families” detected in the site, with others studied in Mesoamerica.
Nevertheless, the architectural, calendrical and symbolic implications of the pre-Hispanic cosmovision are revealed, as well as the intricate autochthonous astronomical features of the specific cultural region of El Bajío. On the other hand, although there are other examples that deal with the functionality of pyramidal structures acting as a hill or artificial horizon, only Rubén Morante (1996) is cited, since he coined such term while working at Teotihuacán in central México.
The different lunar positions shown are intertwined with the rhythm of the sunset, emphasizing the moments when such celestial object rests on the different superimposed bodies of the pyramidal base. Particularly in the corners and slopes where these bodies intersect, creating numerical intervals that have certain qualities of multiplicity with recognizable Mesoamerican calendar units: 20, 13, 5, 52, 65, and so on. Actually, 65 is the interval that became evident as the exercise unfolded. The number appears in terms of years and tens of years, within cycles that could -eventually- be associated with the founding moment of the ceremonial center that concerns us, considering the dates of Carbon recovered by Gabriela Zepeda (2012). As coordinator of the exploration of Cañada de la Virgen, Zepeda emphasized the role of cultural astronomy as a complementary method to explain the foundational dates, along with the moments revealed as differentiated stages of occupation through construction system features¹.
The internal congruence of the presented model explains the importance of the major and minor lunar positions and discusses the appropriate terminology in terms of references to lunar standstills, lunistices or maximum and minimum extremes of full moon.

¹ Personal conversation with archaeologist Gabriela Zepeda. Susan Milbrath discussed the stages of occupation of Templo Mayor in terms of the 52 years of the new fire.