PAGOSA SPRINGS — A blinding bolt of light zigzagged from a leaden sky. A cracking boom thundered three seconds later.

“We need to get everyone off the mountain immediately,” our guide shouted.

My wife and I dived into our parked car and began descending the twisty, 3-mile gravel roadway. A Noah-worthy deluge greeted us as we reached the visitor cabin below.

“It should clear up by tonight,” speculated my ever-optimistic spouse.

Although our afternoon tour of Chimney Rock National Monument had been rained out, we still harbored hope for the evening’s Night Sky: Stars & Galaxies program.  Through the telescopes of local astronomy club members, we would get to peer into the heavens from an astronomical site used centuries ago by the Ancestral Puebloan people.

The monument, which protects a small group of Ancestral Puebloan ruins located 20 miles southwest of Pagosa Springs, is divided into two neighboring sections. The lower ruins feature a community of circular pit houses — so named because they were built partially below ground. About the size of a walk-in closet, each would have sheltered an entire family of farmers who grew corn, beans and squash on the nearby slopes. The paved Great Kiva Trail loops through the area with numerous interpretive signs along the way.

A second set of ruins — only available on guided tours — lie at the top of the rocky Pueblo Trail. Here, high on a ridgetop, an Ancestral Puebloan construction crew built the Great House Pueblo. Using an estimated six million stones, 5,000 logs and 25,000 tons of adobe mortar, they crafted a complex with more than 35 rooms and a pair of ceremonial chambers known as kivas.

The location for such a grand structure puzzled archeologists. No crops could grow here, the nearest water flowed far below and no evidence suggests the site ever served as a high-ground fortification. It ultimately took an astrophysicist from the University of Colorado Boulder to solve the locational enigma.

Every day from the winter solstice onward, the sun rises slightly to the north of where it did the day before. At the time of the summer solstice, that northern progress comes to a screeching standstill. It then shifts into reverse, rising farther to the south each day until the winter solstice.

The moon over time also rises from progressively different spots on the horizon. The northernmost point from which it rises is called a “major lunar standstill.” While the sun does a complete north to south and back again cycle in one year, the moon takes a laggardly 18.6 years to do the same.

Beyond the Great House Pueblo tower Chimney and Companion rocks, a pair of natural stone pillars. From the pueblo, the notch between them appears to form a massive, rock-bounded gunsight.

Using computer simulation, Dr. Kim Malville determined that from the site of the Great House Pueblo, the moon at its northern lunar standstill would rise like a bull’s-eye from dead center in the notch.

With the next lunar standstill not scheduled until 2025, we’ll have to wait to see the phenomena firsthand. Until then, my wife and I will have to settle for peering at distant stars and galaxies from here through telescopes. At least we hoped we would as we returned to the ruins.

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The Night Sky program began with a Chimney Rock Interpretive Association speaker explaining the astronomical significance of the site. He was followed by a member of the Pagosa Springs astronomy club who talked about the stars and galaxies we might see if the clouds parted.

But they didn’t. The only heavenly object anyone saw through a telescope was Jupiter and three of its moons shining briefly through a quickly closing hole in the clouds.

“It should be clear next time we come here,” speculated my ever-optimistic spouse.

If you go

Chimney Rock National Monument is open daily from May 15 to Sept. 30 from 9 a.m. to 4:30 p.m. Admission with guided walking tours run $14 for adults and $7 for children ages 5 to 12. Kiva Trail self-guided audio tours are $10 for adults, $5 for children.

The next Night Sky: Stars and Galaxies program runs Sept. 7. The program costs $12 for adults and $5 for kids with advance tickets (877-444-6777, recreation.gov) strongly recommended. Stargazers can also enjoy similar Night Sky: Our Solar System telescope programs on Aug. 17 and Sept. 14.

Contact Chimney Rock (970-883-5359, chimneyrockco.org) for more information about the site and other special programs they offer.

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