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Astronomers sleuth Ansel Adams’ Autumn Moon

Date of Release: 08/23/2005

SAN MARCOS—No single person in history has done more to reveal the splendor of the American west on film than famed photographer Ansel Adams.

Now, a team of astronomers at Texas State University-San Marcos have applied their unique brand of forensic astronomy to Adams’ Autumn Moon, the High Sierra from Glacier Point, shedding new light on the celestial scene--and rediscovering a long-lost Adams photo in the process.

Texas State physics professors Donald Olson and Russell Doescher, along with Mitte Honors students Kara Holsinger, Louie Dean Valencia and Ashley Ralph, publish their findings in the October 2005 edition of Sky & Telescope magazine.
Solving the Mystery

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.

An Unexpected Discovery
In the course of research, Olson stumbled across something wholly unanticipated: A color version of Autumn Moon, published in the July 1954 issue of Fortune magazine. Adams is best known for his black and white photography, so this color photograph by him was a rare find.

“Imagine my surprise when I turned the page and saw this color moonrise photograph by Ansel Adams,” said Olson. “We checked with several Ansel Adams experts. None of the Adams experts we spoke with had seen this photo--all of us had been totally unaware that a color version of Autumn Moon existed.”

Some additional investigation revealed that beginning in the 1940s, Eastman Kodak commissioned professional photographers to “beta test” new color sheet film, and Adams was one of the photographers who participated in the program. Eventually, the results were published in an article titled “Test Exposures: Six Photographs from a Film Manufacturer’s Files.”

The cloud formations and shadows in the scene matched those in the well-known Autumn Moon, leaving no doubt that the two shots were taken during the same session. By overlaying the two photos and measuring how far the Moon had risen between exposures, the researchers determined the color version was taken at 7:01 p.m. Pacific Daylight Time, roughly two-and-a-half minutes prior to the black-and-white version--just enough time for Adams to change the film holder and adjust the settings on his camera.

Encore Performance
For fans of Adams’ 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 Sept. 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 Sept. 15. 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’ experience from half a century ago.”


[Digital images suitable for print publication are available to accompany this release. Contact Jayme Blaschke at Texas State University Media Relations and Publications at or (512) 245-2180. Upon request, we will send a PDF file of the Sky & Telescope article containing various images, including the FPO image of "Autumn Moon." "Autumn Moon" by Ansel Adams may not be reproduced without permission. To obtain permission, please contact Corbis, Inc. Tel: 800-260-0444 or Once permission is obtained, the credit line Ansel Adams Publishing Rights Trust / Corbis must be included alongside the photograph.]