YOSEMITE NATIONAL PARK, Calif. (AP) _ Astronomers have pinned down the exact time and date that renowned photographer Ansel Adams snapped his ethereal picture, ``Autumn Moon,'' and have determined that the sun, moon and mountains will align in the same positions on Thursday.
The Texas State University astronomers, who have earned a reputation for nailing down historical dates and events, reached their conclusions after poring through celestial history, plotting lunar phases, building a special computer program and calculating shadow angles.
They concluded that Adams snapped the shutter at 7:03 p.m. on Sept. 15, 1948 _ not in 1944 as was long believed.
Yosemite officials expect a crowd of photographers, astronomers and Adams aficionados will gather atop Glacier Point to relive the scene that Adams captured. The scene repeats every 19 years.
``It's interesting that astronomy can do this,'' said Matthew Adams, the photographer's grandson and president of the Ansel Adams Gallery in Yosemite. ``And it's great that there's this ongoing interest in Ansel. We're planning to go out and see it for curiosity's sake.''
``Autumn Moon: the High Sierra From Glacier Point'' depicts a gauzy moon hanging in the darkening sky above the jagged peaks of the Clark Range.
In 1994, the ``forensic astronomers'' led by astrophysicist Donald Olson pinpointed the moment Adams shot his famous photograph of the moon rising over Half Dome in Yosemite Valley.
They also have nailed down where Vincent van Gogh set up his easel to paint some of his famous celestial portraits, and determined that a Marine Corps landing craft became beached in the South Pacific during World War II because a rare lunar cycle caused an extremely low tide.
Adams died in 1984.