2009 Conference -- Camp Verde, Arizona

Archaeoastronomy is usually approached from the perspective of the archaeologist, anthropologist, or astronomer. This paper proposes a framework for looking at traditional astronomies from the perspective of the historian of science. From this perspective, traditional astronomies employ observations of the place and time of astronomical events to develop spatio-temporal concepts. These concepts guide further astronomical observations, regulate ritual and economic activity, and are employed in myth, art, music, and ritual.

A mathematical model of the Sun Dagger Site at Chaco Canyon is constructed and used to analyze the dynamic features of the sun dagger pattern that occurs at summer solstice. The abstract model supposes straight-line shadow casting edges with spatial orientations and a carefully chosen parameterization of these orientations that is highly faithful to the actual site but still amenable to closed-form mathematical analysis. The parameterization was developed using data and observations obtained from the SD Explorer Model, a fully realistic and interactive computer model of the Sun Dagger Site developed by Sofaer et. al. The latter model is based on a finely resolved laser and photogrammatic-based reconstruction of the site and its surroundings. The development of SD Explorer Model and its interactive application will be briefly demonstrated at the outset of the presentation. The abstract mathematical model derived from the SD Explorer data is shown to capture the essential features of the site’s sun dagger image sequence at summer solstice, such as the emergence of the dagger from a point and its downward and slightly rightward motion. Analysis of the model’s behavior as a function of parameters helps to clarify the design and operation of the site. In particular, it reveals the crucial importance of strongly eastward site orientation and the dimensions and placement of cliff overhang feature above the site that have not been emphasized before.

Two clusters of axial orientations of pit structures in Chaco Canyon appear as early as A.D. 600 in Shabik’eschee village. These orientations, which were either north-south or rotated 25° east of south, may have developed from early nomadic traditions. A century or more later, the same duality appeared in the northern San Juan in villages along the Dolores River, such as McPhee and Grass Mesa, suggesting differences in ethnicity. The basic pattern was that of the Prudden unit-type pueblo, with a roomblock to the north of a proto-kiva or kiva. Many of the Greathouses in Chaco continued this “front oriented” alignment toward the south and SSE. A radical shift of perspective to alignments ninety degree from the major axes is not justified either by archaeological theory or data. All of the proposed astronomical alignments along the back walls of Greathouses may be the coincidental and unintended consequences of their front orientations. Major lunar standstills appear to have been first discovered and celebrated at the Chacoan outlier at Chimney Rock. Proposals of lunar standstill alignments in Chaco Canyon do not survive scrutiny using current measurements. The three-slab site on Fajada butte, which marks June solstice with the “sun dagger”, was probably associated with the 13th century “pinnacle site” near its summit, but not with the Chacoan Florescence. Astronomy appears to have served the needs of Chacoan society by providing a ceremonial calendar for periodic festivals and pilgrimage, a background for ritual performance, and a technique for establishing true north.

Archaeologists differ about the relative importance of political power, ritual activities, trade, and pilgrimage in the Chacoan regional system. Nonetheless, there seems to be agreement that visual astronomy played a role; at least to provide a calendar for periodic events. We describe locations in Chaco Canyon that may have served as primary calendrical stations for establishing dates to anticipate and confirm the solstices, as well as identifying the full moon closest to solstice. Most of these sites are associated with December solstice and are contained in or close to Late Bonito structures such as Wijiji, Kin Kletso, and the Headquarters Unit. The calendrical station at Piedra del Sol could have provided the dates of June solstice necessary for positioning the spiral petroglyph of the Fajada Butte three-slab site. The highest point of West Mesa as viewed from the great house of Casa del Rio may have been a very early winter solstice marker. An intriguing site for observing December solstice sunrise is close to two ruins which range in occupation dates from A.D. 900 to 1200, located southeast of Wijiji and excavated by Roberts in the 1920s. This site contains Puebloan and Navajo cultural material, and may have been associated with Basketmaker III or early Pueblo I occupation of Shabik’eschee Village. A visual communication system supporting organization of calendar-driven community ritual may have extended from the shrines of West Mesa to the eastern edge of Chaco Canyon near Wijiji. We suggest a protocol for identification of possible Chacoan calendrical stations

Casa Rinconada, located at Chaco Culture National Historic Park in northwestern New Mexico, USA, has been found to have very unique and sophisticated lunar alignments to complement its already reported directional and solar orientations. This large round building within itself hints at a level of lunar understanding and architectural design refinement not before suggested for these ancient people. This presentation and paper will focus on detailing the mechanics of the various alignments with and emphasis on the newly discovered lunar aspects. While these many alignments function today in the 1000 year old ruin that has been partially rebuilt in modern times, there are many questions to be considered prior to inferring intentional encoding of this astronomic knowledge by the original ancient builders. This presentation will also present the evidence from the site and elsewhere that confounds conclusions of intentional encoding of this lunar information by the original builders.

We propose that in and near Chaco Canyon, New Mexico, numerous C-shaped sites and two cairn sites may have been intentionally interrelated on alignments to the major standstill moon. These sites are located on the tops of Chacra, South and West mesas and a mesa seven miles northwest of Chaco Canyon. We will present maps, photographs and survey data documenting these possible lunar inter-site relationships. The lunar standstill cycle has been studied and documented by the Solstice Project at the Sun Dagger site on Fajada Butte in shadow markings on a spiral petroglyph and in the alignments of seven major Chaco buildings, as well as in certain inter-building relationships. The research documenting the architectural alignments was conducted with NOAA’s National Geodetic Survey. Research by others has also shown that Chimney Rock Pueblo, a Chaco building ninety miles north of Chaco Canyon, is related to the major standstill of the moon.

Over the last five decades, dozens of star/crescent combinations in rock art, particularly in the Southwest and California, have been identified as depictions of the Crab supernova, which was observed and recorded by Chinese astronomers in 1054 A.D. This interpretation originated in 1955, with reports and commentary by William C. Miller on two sites in northern Arizona identified by Miller as White Mesa and Navaho Canyon [sic]. Although the rock art Miller described precipitated a lasting trend of supernova association with star/crescent imagery, the two original panels of alleged supernova rock art had not been re-examined for more than 50 years until the authors established exact locations for these remote sites and reached them in May, 2008. These visits provided an opportunity to see and evaluate the panels in context and prompted reconsideration of the supernova explanation for this rock art.

We tested the hypothesis that there is a relationship between architecture and observable astronomy by investigating overall layout, regularity of form, size, construction cycles, and feature placement utilizing a rigorous standardized architectural documentation system and direct observations. Research on lunar standstills at Mesa Verde National Park was conducted at Cliff Palace and Sun Temple in 1990-91. Those studies proposed alignment of architecture for the purpose of observing the Southern Major Lunar Standstill moonset over Sun Temple from Cliff Palace. The alignment was suggested by mathematical modeling and fieldwork.

We completed a detailed architectural analysis at Sun Temple which supports the hypothesis that the lunar maximum was observed over Sun Temple from the Painted Tower area of Cliff Palace. Tree ring dates at Balcony House and Square Tower House suggest a relationship between construction of specialized architecture such as kivas and the lunar maximum cycle. The results of the research assess the correlation of the lunar standstill cycle with major architectural features, structural form and placement, and construction phases. This will contribute to the development of new social models evaluating how the evolution of science in ancestral societies affects their social structure. We may be able to make inferences about the cycle of social interaction, resource allocation, extent to which astronomical information was used, and other socio-ceremonial activities of the Ancestral Pueblo people of the Mesa Verde.

Among the many mythic, lithic, features of the landscape in Navajo (Diné) country, Sonsela Buttes located near beautiful Canyon de Chelly, has particularly interesting significance from the standpoint of Diné tradition, geography and geology. Indeed, from the traditional point of view, one could even say that they are significant in cosmogony. A Diné story and accompanying lore suggest that when Coyote flung stars across heaven some fell back to earth and landed where Sonsela Buttes now stand; thus the name, meaning "stars lying down." A layer of sandstone dating to 227 million years ago, responsible for depositing and protecting the world's most famous and beautiful petrified wood within what is now Petrified National Forrest, also bears the name Sonsela. This paper explores relationships between legend and geology relating to Sonsela Buttes.

The Hohokam Culture of the Sonoran Desert is well known for its large irrigation systems and its public architecture, including hundreds of ball courts and platform mounds. For more than a millennium, Hohokam farmers practiced a sustainable lifestyle in an arid environment. This long-term successful adaptation was due to their ability to organize large work crews during seasons of intensive labor demands, as well as to maintain some sense of social, political, or cultural cohesiveness among diverse groups spread across the desert landscape. Tracking time would have been important to these desert farmers, both to assist in the scheduling of labor activities and for maintaining ritual cycles that structured their view of the universe. It is not surprising that archaeoastronomy studies over the last two decades have determined that the Hohokam had solar calendars involving rock art and architectural markers, and they probably observed the patterns of other celestial bodies in the night sky. This paper reviews what is currently known about Hohokam astronomy, including research done on rock art light and shadow patterns, horizon alignments, and solar eclipses

The many years of research by Jerry Howard and others on the prehistoric canal systems of the Hohokam in the Salt River Valley in South central Arizona give us an insight into the engineering abilities of these early people. The research shows that these canals have an almost perfect grade for moving water over long distances following the curvatures of the land without eroding the bottom away or allowing much sediment to build up. All these factors would seem to indicate that these people possessed a devise of some type to survey the land and determine the grades.

This is also true with the research of prehistoric astronomy in the same area. The Hohokam people divided the horizon between summer solstice and winter solstice into four equal parts. They determined these alignments for both sunrise and sunset. The location of the equinox’s alignments was within ½ a degree of center between the solstice alignments and the locations of where many of the 37 mound sites were placed on these alignments.

The research presented in this project reviews both the archaeological record and the ethnic record to determine what type of devices might have been used and what tools and other knowledge might have been needed to produce the results found in the archaeological record of the Southwestern United States.

There have been numerous archeoastronomical studies in other prehistoric areas of the American Southwest, but in the Mogollon this research has languished. This paper attempts to address this shortcoming and to make some modest inferences that are broadly in tune with other current archaeological research in this area. The Gila Cliff Dwellings is the only National Monument representing the Mogollon culture and because of its protected status, it was a natural candidate for astronomical research. During the past three years, I have conducted archaeoastronomy research in and around the Gila Cliff Dwellings. Adobe Canyon is a small NE/SW facing canyon that empties into the Gila River about a mile below Cliff Dweller Canyon. The mouth of the canyon is marked by a number of pictographs, which include; negative handprints, deer or quadrupeds, a crescent moon, and a rectangle box. These pictographs are placed strategically around the mouth of the canyon to provide sun and moon watching stations. The canyon provides a natural calendar, which marks the rising summer solstice sun and the winter solstice sunset. I have been documenting the entire sequence of rising and setting full moons as well as rising and setting solstice suns.

The historic sunwatching practices of the Hopi have been well documented. There are abundant Hopi migration traditions that discuss events and places within the prehistoric Southern Sinagua region of north central Arizona, including the sunwatchers of the Patki and Sun clans. This study documents some of the many solar calendric devices of the Southern Sinagua using petroglyphs and pictographs. The Patki Clan symbol, found in association with several of these devices, provides a link to historic Hopi. In addition, several probable horizon observation points for determining the time to engrave the rock art images have been located. Sun shrines, of similar structure to Hopi and Zuni shrines, used to mark the sunrise positions on the horizon have also been identified

Picture Canyon is part of Northern Arizona University’s Centennial Forest in Northeastern Flagstaff, AZ. Two pueblos within a mile and a half of this site were occupied from approximately 1100 to 1300 AD. At the east entrance to the canyon, on the first volcanic boulders with petroglyphs, is an east facing five-turn counter-clockwise spiral. Vertically, it measures 16 inches and 15 inches across. Four and one-half feet to the east is a shadow projecting rock, which throws a light/shadow line diagonally across the spiral at sunrise. The shadow line moves across the spiral, right to left, between spring equinox (90 degree azimuth) and ten days after the cross-quarter, in mid May (66 degree azimuth). This transit takes 56 days. This is repeated going left to right between July 27 and Fall equinox. The shadow projecting rock is shaped so that it follows the arc of the rising sun on the eastern horizon. This feature causes the shadow line to remain in the same position on the spiral for about 50 minutes after zero altitude sunrise. Preparation for planting in this local area may have been marked in mid-May when the shadow line is tangent to the left side of the spiral. The full moon at the northern minimum lunar standstill position will also cast a shadow line tangent to the left side of the spiral

In our efforts to promote the highest professional standards for field work in Southwestern Archaeoastronomy we would do well to be mindful of important lessons from our own discipline's past. Among the most prominent and powerful of these are three that were products of the work of archaeoastronomers at Penasco Blanco, Wupatki Pueblo, and Casa Rinconada.

Although the matter seemed to have been settled in 1975, some 21st century writers who have written about the Penasco Blanco "supernova" site apparently still have not perceived the substantial weight of the ethnographic evidence that has been brought to bear on it. In fact scholarship about these pictographs did produce a potent case study that shows why it is imperative that we employ well-defined ethnographic evidence.

Wupatki Pueblo provided us with a conspicuously clear case study concerning the importance of obtaining all pertinent historical records and documents about a site. Interpretation here hinged on the matter of the presence or absence of a single architectural feature (a window) for which there actually is documented evidence.

At Casa Rinconada the primary concern was about the exactness of the size, shape, and location of a specific feature (an opening in a wall) rather than its presence or absence. The feature was known to have existed prior to this Great Kiva's reconstruction. The hard-line lesson here is that the chanciness of the reconstruction sabotages confidence in arguments about the intentions of the original builders.

Photographic documentation has the power to persuade even the most serious of skeptics concerning the sophistication of ancient astronomical knowledge. The testing of hypotheses concerning the horizon sun and moon by a camera is a vital element in archaeoastronomy, and we present cases where suggested horizon events have been disproved as well as confirmed. While it is important to support the assertion of structural alignments and the astronomical purpose of specific sites via cultural tradition, it is the photograph that provides the most convincing evidence, pro or con. Because sunrise and moonrise photography places the modern observer in the same setting as in the past, it can lead to a deeper understanding of the full meaning of these events for ancient people. We discuss the use of photographic documentation of horizon events taking into account issues such as the changing obliquity of the ecliptic, identification of observing site, symbolic importance of the landscape, and public/private access to the ceremony. Solstice sunrises are not useful for correcting the calendar but they can provide impressive ritual drama and opportunities for social integration. In the Chacoan world visual impact was an important feature of the placement of great houses, and we assume visual drama was important in the communal viewing of astronomical events. We will present photographic examples of solstice and lunar standstill events at Chaco, Chimney Rock, Comb Ridge, Hovenweep, Mesa Verde, Yucca House, and Yellowjacket, describe their significance, and the technical circumstances under which the photographs were made.