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Needs to be condensed and reworded (to avoid copyright issues) before addition ... to the last section:
At summer solstice in 1977, Anna Sofaer, while studying petroglyphs on top of Fajada Butte, witnessed a dagger shape of light cast by the opening of two large rock slabs bisect the center of a large spiral carving on the rock wall behind the slabs. This site, subsequently called the Sun Dagger site, was created approximately a thousand years ago by the ancient Pueblo culture of Chaco Canyon. In 1978, Sofaer established the non-profit Solstice Project dedicated to the study and preservation of the achievements of the Chaco Culture and the dissemination of educational information about it and other cultures of the American Southwest. From 1978 through the 1980s, the Solstice Project's research on the Sun Dagger site showed that it marked the key positions of the solar and lunar cycles: the summer solstice, winter solstice, and equinox; and the major and the minor lunar standstills of the moon’s 18.6 year cycle.
The Solstice Project also conducted through the 1990s extensive research on the Chaco people’s expressions of astronomy in architecture, road constructions and light markings on other petroglyphs. These studies revealed that two other petroglyph sites on Fajada Butte are marked with light patterns distinctive to the solstices and equinoxes at solar noon. They also documented with the National Geodetic Survey of NOAA (spell out?) that twelve major Chaco buildings are oriented to the extremes and mid positions of the solar and lunar cycles, the same positions that are marked on Fajada Butte. In addition, they found that the interbuilding bearing of these major buildings are also aligned to the sun and the moon. Corresponding findings were documented at an outlying Chaco site, Chimney Rock, showing that it was situated for its alignment to the rise of the major standstill moon. Other research of the Solstice Project showed that the Chaco people incorporated solar-lunar geometries in their fourteen major buildings.Finally, its studies of the Great North Road, a 35 mile engineered “road”, revealed that it was probably developed for the purpose of connecting the ceremonial center of Chaco Canyon to the the direction north -- a most sacred direction to the descendant Pueblo cultures.