Chaco Canyon in the remote high desert of northwestern New Mexico was the spiritual and scientific center of a civilization that covered the entire four corners region of the American southwest. Unlike later pueblos in places like Mesa Verde and Montezuma's Castle, the great houses of Chaco were centers for astronomical observation and cultural activities with small permanent staff. They attracted thousands of visitors from across the region that traveled to Chaco Canyon on a road network that spanned hundreds of miles for special events. The climate changed devastating agriculture in most of the region and the population and focus of civilization in the southwest migrated to regional ancestral puebloan centers in locations like Mesa Verde in Colorado, ancestors of the Navajo and Hopi in Arizona, and the pueblos that survive along the Rio Grande today in New Mexico.

In 1977 Anna Sofaer discovered the Sun Dagger on Fajada Butte while recording petroglyphs. Two 2-3 meter high vertical slabs of rock with curved surfaces, interact with sunlight on the summer solstice to cause a dagger shaped shaft of light to move vertically through the center of a spiral petroglyph. Later observations confirmed that the 19 year lunar cycle is also captured, and nearby stone instruments capture the equinoxes.

Today the Chaco Culture National Historical Park is a UNESCO World Heritage Site and an international Gold-tier Dark Sky Park.

Above is my two exposure HDR capture of the crescent moon rising over Fajada Bute before dawn on October 4, 2021 from near the south entrance to the park. I was able to watch the moon from first glow to the left and as it moved up and over the butte. This HDR 2 exposure image taken with a 50mm f/2.8 lens and Sony a7iii camera captured scene at 2021-10-04 12:02 UT with f/2.8 exposures of 4/3 and 2/3 sec.