The Crestone Eagle • September, 2020 

Skies Over Crestone: Autumnal equinox

by Kim Malville

This month contains the autumnal equinox, which occurs at 8:31amMDT on September 22.  Neglecting the effects of atmospheric refraction, on a flat horizon the sun rises due east on the morning of equinox. September also has great planets. Venus rises 3 and a half hours ahead of the sun and reaches an altitude of almost 40° above the eastern horizon.  Mars rises about two hours after sunset at the start of the month and less than one hour at the end. It starts the month about half as bright as Jupiter, but brightens as Jupiter fades, becoming brighter by the end of the month. Jupiter and Saturn are high in the southern sky a few hours after sunset in the constellation of Sagittarius.

September 2: Full moon.

September 5: The moon comes within a half-degree south of Mars about 10pm. Watch the gap between them close starting earlier in the evening.

September 9: Mars starts moving retrograde.

September 12: Jupiter halts its retrograde motion and begins moving eastward.

September 22: Equinox.

September 24: After sunset the moon, Jupiter, and Saturn form an arc across the southern sky.

September 25: The moon, Jupiter, and Saturn form a triangle

Celebrations of Equinox


Chichen Itza

At Chichen Itza in the Yucatan Peninsula, during the spring and fall equinoxes, shadows of the sun create a serpent creeping down the northern staircase of the pyramid of El Castillo dedicated to Quetzalcoatl, the feathered serpent of Mayan and Aztec myth. Symbolically, the serpent descends and joins heaven, earth and the underworld. Thousands of people gather to admire and cheer this astronomical spectacle. The plaza around the pyramid becomes alive with rock bands competing with traditional music, elaborately clad folk dancers, and new agers robed in white to attract positive energy from the sun. The late afternoon sun hits the northwest corner of the pyramid and casts a series of triangular shadows against the northwest balustrade, creating the illusion of the feathered serpent crawling” down the pyramid. Chichen Itza in the Mexican state of Yucatán was built sometime between the 8th and 12th centuries CE. Ironically, it’s not certain that the builders of the pyramid has envisioned this spectacle.

Angkor Wat

Angkor Wat is a temple complex in Cambodia and may well be the largest religious monument in the world, on a site measuring 402 acres. The initial design and construction of the temple took place in the first half of the 12th century, during the reign of Suryavarman II who ruled from 1113 to ~1150 CE. Dedicated to the Hindu god Vishnu, it was built as the king’s state temple, capital city, and, like to the great Egyptian pyramid of Kufu, also his tomb. It was eventually transformed into a Buddhist temple, with images of the Buddha replacing that of Vishnu in the central shrine. It has become a symbol of Cambodia, appearing on its national flag, and it is the country’s prime attraction for visitors. In 1993, there were only 7,650 visitors to the site; by 2018, the number of visitor exploded to 2.6 million, especially coming at spring and autumn equinoxes. 

Angkor Wat combines a temple representing five peaks of Mount Meru, which, like Mt. Olympus, is the home of the Hindu gods with a huge moat more than 3 miles long. In Hindu tradition, the center of the world contains Mt. Meru surrounded by a vast ocean, which is represented by the moat.   Unlike most Hindu temples in Cambodia and India, Angkor Wat is oriented to the west, which, inadvertent or not, provides celebrants (and now thousands of tourists) with spectacular views of the sun rising over the top of the highest spire on the two days of the equinoxes. This sight was apparently intended by the builders. The axis of Angkor Wat has been rotated by 0.5° away from east-west such that the sun on the morning of equinox rises over the top of its highest spire.

In Hindu and Buddhist temples and shrines, one circles the center in a clockwise direction.  In Angkor Wat, the story lines of carving on the walls carry the viewer in a counter-clockwise direction. The remarkable oppositions of this temple to most of those in Southeast Asia in movement about the temple and its orientation to the west reveal that Angkor Wat was intended to be a temple of the underworld, a mausoleum for the king.  Another amazing feature of Angkor Wat is that the highest spire once a hole in its capstone, allowing sunlight to enter its dark interior when the sun was directly overhead at the zenith. The sun can reach the zenith only at those latitudes between the Tropics of Cancer and Capricorn. At Angkor Wat, the sun reaches the zenith on August 17 and April 26, which appear to be two days in addition to equinoxes that were significant in the temple. For better or worse, restorers have closed the hole in the capstone to prevent rain from entering the structure. What is even more remarkable, there was a shaft 6” in diameter leading downward for 89’ to a sarcophagus in the tomb of Suryavarman II. In that sarcophagus there was a small hole that may have allowed light of the sun, falling a total of some 200 feet from the capstone, to touch the body of the king on the two days of the zenith sun. Was the light of the sun intended to bring life back to the deceased king? What amazing astronomical-mortuary science lies behind it beautiful architecture! If Angkor Wat is in your bucket list of wondrous sites of the ancient world to visit (which indeed it should be) the best time to visit is probably not the spring or fall equinox, unless you love crowds.