There was frost on the tent when we awoke at 5 a.m. As we climbed back up to the tripod location, the landscape felt newly familiar. All the uncertainty of the dark dissolved, like shadows in a nightmare.
Now I saw the view as Adams had seen it. Although I couldn’t yet know for sure, I suspected he had been heading up to Elizabeth Pass when he was surprised by the sudden view of Horn Peak cutting into the blue sky. As the sun rose behind me, a black curtain of shadow slid down the cliff. The wonder I felt at discovering the peak at sunset, hidden at the top of the canyon after many miles of invisibility, must have been punctuated for Adams by the perfect placement of the moon.
Back at home, I sent the photographs to Dr. Olson, who set to work.
“Knowing the date and time of the modern star-field photograph,” he explained in an email, “we identified the constellations and calculated the altitudes (height above the horizon) and azimuths (compass directions) of many visible stars.”
Once the team identified the region of the sky included in the Adams photograph, they used “computer planetarium programs to search the 1920s and 1930s for dates and times when a waning gibbous moon, with illuminated fraction near 85 percent, passed near this position in the sky,” Dr. Olson wrote. The search had originally turned up four possible dates. Using documentary evidence in the Ansel Adams Archive and lunar libration, a phenomenon that “affects the visibility of lunar surface features,” according to Dr. Olson, they narrowed down the possibilities. They concluded that Adams had made “High Country Crags and Moon, Sunrise, Kings Canyon” at 6:47 a.m. on Aug. 6, 1936.
On that date, the Sierra Club’s High Trip was nearing its end. Louise Hewlett, the trip recorder that year, wrote, “Leaving Elizabeth Pass was like closing the door upon the High Country — for another year, at least from that moment we moved steadily on, over improved trails, toward our starting point — toward automobiles, roads, houses.” Adams, too, was moving steadily onward with the Sierra Club toward home, but also toward new heights in his career.