Thu. Aug 25, 2005
Ansel's Autumn Moon
Glacier Point in Yosemite National Park is one of the most awesome viewpoints in this country. Anyone with an eye for stunning vistas is drawn to the place. Like Ansel Adams. And it turns out that I made a very small contribution towards the effort to find out the exact details of one of his more famous shots.
Texas astronomers have pinned down the exact date and time that a famous Ansel Adams photograph was taken.
Although Adams took detailed notes on the exposures for his works, he was often frustratingly vague about when and where the shots were taken, says team leader Donald Olson. But Adams’s love of sky phenomena, particularly the Moon, sometimes provides enough clues for a little astronomical sleuthing.
“The Moon with its rapidly changing phases and position is really a big cosmic clock,” says Dennis di Cicco, an editor at Sky & Telescope magazine. “When you’ve got a picture with a Moon in it, you can do these calculations.”Nature: Astronomers date Ansel Adams photo – Lunar clues reveal when the snap was taken.
And here Ansel’s shot. Now, how did I get involved? Simple. I just answered my e-mail. Last November, I got this one from Donald Olson, the team leader:
If you can find the information without too much trouble, can you tell me on what calendar date (and time, if you camera’s internal clock time is on the original file) when you photographed the moonrise over the High Sierra?
My students and I are studying in detail some Ansel Adams moonrise photographs, and the more data we collect on Glacier Point, the better. We have a computer program to study Ansel Adams moonrise photographs, and we could use your photo as a test case to make sure that our program is running correctly.
After some serious racking of the brain over a decade old photo (it took an old calendar and a lot of pondering), I determined that I did the shot on Wednesday, August 9th, 1995, between 8:15-8:30pm (this was long before the days of digital and time stamped images). But I’m apparently not alone when it comes to a lack of notes.
Adams kept detailed notes on the technical aspects of his photographs — exposure time, film type, lens settings — but information about the location, date, and time of his images was often incomplete or contradictory. Such is the case with Autumn Moon, taken by Adams in Yosemite National Park and featuring a waxing gibbous Moon rising over mountains of the Clark Range in the southeast. Various sources give the date of the photograph as 1944, while others list it as 1948. After consulting lunar tables, topographic maps, weather records, and astronomical software, the Texas State researchers determined that Adams created Autumn Moon on Sept. 15, 1948, at 7:03 p.m. Pacific Daylight Time.
As part of their research, the group visited Yosemite in the spring for extensive on-site double-checking of their findings. Additionally, the team determined that Adams had set up his tripod just off the trail below the stone Geology Hut at Glacier Point, pinpointing the location to within 10 feet. Olson and Doescher, along with another team of honors students, used similar techniques in 1994 to pinpoint the time, date, and location Adams photographed his famous Moon and Half Dome.
For fans of Adams’s photography, 2005 offers a rare opportunity to relive the scene of Autumn Moon — both color and black-and-white versions. This year, the progression of 19-year-long lunar Metonic cycles coincides with that of 1948 — meaning that skywatchers at Glacier Point are in for a celestial encore. On September 15, 2005, exactly three Metonic cycles will have passed since Adams photographed a waxing gibbous Moon rising over the Clark Range, presenting a scene that will closely duplicate the one in 1948.
“Even the direction of sunlight and shadows will be repeated this year,” said Olson. “Our group plans to be on Glacier Point when the Moon’s position will match the Adams photographs at 6:50 p.m. and 6:52 p.m. Pacific Daylight Time on September 15th. The balance of light between the rising Moon, the setting Sun and the shadows in the foreground mountains will last for just a few minutes and will provide a rare opportunity to share Ansel Adams’s experience from half a century ago.”Sky and Telescope: Astronomers Date Ansel Adams’s “Autumn Moon”
And I would give almost anything in the world to be there.
Later: Here’s the most complete article I’ve seen on this topic, by Eric Bailey in the Los Angeles Times: History to Repeat Itself at Yosemite. Of course, I may be biased by the small mention of yours truly.