This essay concludes the Special Section “Mesoamerican Cultural Astronomy and the Calendar.” In it, the themes Special Section authors address are put into both an anthropological and an astronomical context.

Members of the Proyecto Arqueológico de la Biosfera Calakmul under Carrasco's direction excavated the Cenote Style Group E-type complex at the Maya site of Calakmul, Campeche, Mexico. The Cenote Style refers to the plan of the E-Group with a series of three temples built onto a long narrow eastern range structure facing a western structure across a broad central plaza. Architectural data exist to evaluate this standardizing group's utility for observing solar events. Astronomical evidence for the function of this complex is presented and discussed. The overall orientation of Structures IVa, IVb, IVc, and VI is slightly east, 13° of true north, while a pair of doorways in Structure IVc align with the setting sun during the summer solstice point, despite the break in the buildings' floor-plan symmetry this represents.

This study places the recently excavated ninth-century A.D. four-part calendrical notations at Xultun (Lunar Table, Ring Number, Long Count, and Multiplication Table) in the context of both Classic monumental inscriptions and astronomical knowledge in the Postclassic Dresden Codex. We demonstrate that the Lunar Table employed a formula attributed to Palenque and that it could have been used as a device to determine precisely where to break the sequence of alternating 29- and 30-day months one finds on dated monuments. All four categories found at Xultun appear in the Dresden Codex. The Ring Number, which bridges a date in the deep past with one in the recently completed era, is a perfect fit with one of the most fundamental Dresden eclipse cycles. Our analysis of glyphs accompanying the Long Count date enables us to place candidate eclipses, especially one that corresponds with a conjunction of Mars, in real time. We argue that the large multiples were extracted from, or prepared for, warning tables like the Dresden eclipse table, and we demonstrate why such tables must have existed well before the Xultun inscriptions. Thus, while the writings in the Dresden manuscript constitute a finished product, the writing on the wall of residential Structure 10K-2 is more akin to what one might find in an astronomer's notebook.

One tends to think of the study of pure number as an esoteric pursuit. But for the ancient Maya, particularly when it came to temporal matters, numbers were more than mere devices to tally units of time. In stark contrast to the Western calendar, in the Maya realm of timekeeping the duration between ritual events seems to have mattered as much as the times when the events themselves occurred. Moreover, the manner in which the daykeepers of the Maya codices sequenced the intervals followed well-defined patterns, which reveal an array of motives for the Maya way of structuring time. Among these motives were the need to: a) arrive at or avoid particular lucky or unlucky days; b) accommodate changing seasonal or other astronomical events; and c) set up numerological mirror symmetries, a characteristic that resonates with the Pythagorean philosophy of number. Thus the long-neglected study of Maya number offers insight into the chronological structure underlying ritual process, which finds parallels in contemporary Maya culture.

Long before they devised a written calendar, the Maya articulated their seasons by means of an “orientation calendar” that consisted of visual alignments involving their architecture. One specialized set of buildings, Group Eat Uaxactún, Guatemala, in the Petén lowlands, has been regarded as the prototype of such a calendar. We present new data based on precise measurements made in the field at 12 Group E complexes and obtained for a number of additional sites from reliable maps where on-site astronomical fixes were acquired. Statistical analysis of the resulting 99 alignments supports the hypothesis that, at least at some stage of development, certain of these specialized complexes did indeed function astronomically. The earliest version of the orientation calendar seems to have developed in the Petén; it was focused on the solstices. A later orientation calendar seems to have functioned principally during the season leading up to the onset of rain and crop planting. It consisted of a division of the dry season into 20-day months prior to the first annual passage of the sun across the zenith (approximately May 10 in the Christian calendar). We argue that this later orientation calendar was derived from Teotihuacan during the Early Classic period (A.D. 278–593).

In this paper, we present a complete list of eclipses documented in the Mexica manuscripts. We use this list together with information in the chronicles to outline a possible method used by Mexica chronologists for linking historical with retrodictable cosmic events that were deliberately chosen to fit historical circumstances. Solar events, particularly eclipses, figure prominently in a scheme that stresses the recurrence of like-in-kind events positioned at multiples of the Xiuhmolpilli (52-year) cycle. Thus, both the foundation of the empire and calendrical adjustments related to the fictional chronology of World Ages are connected to eclipses that were visible at Tenochtitlan and that fell either at the solstices or the equinoxes.

We have empirically tested and evaluated several astronomically related hypotheses about the ruins of Alta Vista near the modern town of Chalchihuites, Zacatecas, in Northwest Mexico. We conclude that the site was deliberately located and oriented astronomically by people of the Teotihuacan civilization.

As supporting evidence we analyze (a) a double solar alignment incorporating a labyrinthine hallway at the ruins, and (b) a pair of circle-shaped markers, of a type found at Teotihuacan, pecked into a flat stone on a hilltop to the south. The former can be correlated with an equinoctial sunrise observation and the latter with a summer solstice sunrise, each over the same distant peak. Furthermore, a detailed examination of the pecked petroglyphs reveals that they may have served as time-marking devices.

A tendency for many precolumbian buildings to align east of north is examined for possible astronomical motives. Stellar and solar phenomena are suggested as possible influences. The importance of clearly establishing the relative positions of observer and point of reference in any archaeo-astronomical analysis is emphasized. Certain misconceptions concerning chronological correlations of alignments and a new dimension in establishing orientations are discussed.

Tables are presented which give the rise-set azimuths of prominent celestial bodies and the heliacal rise-set dates of bright stars for a combination of epochs, latitudes, and horizon elevations.

Mound J, Monte Albán, a building of peculiar orientation and shape, has been mapped and tested for astronomical orientation. At the time of construction of the building, a line perpendicular to the base of the steps of J would have pointed to the rising position of the bright star Capella, which rose heliacally on one of the days of solar zenith passage. We note the existence of a possible zenith sighting tube built into the steps of building r which lies in the line of sight. A second coincidence is discussed in which 5 of the 25 brightest stars are found to have set close to the azimuth of the "point" of the building at the time it was erected.