YOSEMITE NATIONAL PARK — From Glacier Point’s perch, the view deep down into Yosemite Valley is one of the park’s most stunning.
But clusters of Bay Area amateur astronomers are instead pointing their telescopes toward the heavens, where an inky black sky holds planets, asteroids, nebulae and galaxies.
These weekend “star parties,” hosted by local astronomy clubs in Glacier Point’s stone amphitheater, are a 35-year summer tradition in Yosemite National Park.
In exchange for sharing their equipment and expertise with the public, amateur astronomers get free entry into Yosemite — and coveted camping spots.
“It is the absolutely perfect place,” said Dave Balogh, a now-retired Yosemite park ranger who in 1973 first brought his telescope to the granite outcropping on the south wall of Yosemite Valley. He then conceived of the idea to invite outside volunteers, expanding public access.
The Peninsula Astronomical Society, the San Jose Astronomical Association and the Santa Cruz Astronomy Club all plan star parties in early August, when skies are the darkest.
Equipment ranges from humble binoculars to a 24-inch telescope that is so powerful it can discern sights such as the Ring Nebula, an expanding shell of gas emitted by a dying parent star.
The clubs also present a “sunset talk” — usually a slideshow about fun astronomical facts — while visitors are gathering but before it is fully dark.
“It is 7,000 feet up,” said William Phelps of the Peninsula Astronomical Society. “That’s 7,000 feet less atmosphere to scatter the light. And it’s a long way from any cities. But you can drive there.”
In the bright and busy Bay Area, for instance, you often just see ordinary single stars when you gaze upon the cross-shaped constellation Cygnus the Swan. But Glacier Point’s clear dark skies and powerful telescopes reveal Albireo — a beautiful “double star,” with the brighter star gold and the dimmer star blue. Nearby, you can even spot the tiny “Coathanger Cluster,” with four stars as the hook and six stars as the bar.
Also on display are Mars, Jupiter, Saturn, the Andromeda Galaxy and the magnificent “Double Cluster,” each containing supergiant suns, in the northern part of the constellation Perseus.
By 11 p.m., a white veil arcs overhead. It’s the Milky Way — “a couple hundred billion little flashlights,” said Phelps, a Palo Alto resident whose club will bring 10 telescopes, then celebrate Sunday morning with a festive pancake breakfast.
Visitors are encouraged to bring flashlights to avoid a dangerous fall. But cover the light with red film so that your eyes stay “dark adapted.”
Overwhelmed by the enthusiasm of visitors who sought a glimpse through his single telescope, ranger Balogh convinced the park service in 1983 to let amateur astronomers bring telescopes and share them with the public.
With just his one scope, “the number of people who came to look through it was unbearably large,” he recalled. “People would get a quick glimpse, and I’d have to say, ‘That’s it for you.’
“My idea is: It’s their hobby and they love to share,” he said. “And the public gets to look through many telescopes, not just one.”
The National Park Service also offers astronomy talks in Yosemite Valley, Tuolumne Meadows and Wawona.
Over the years, the clubs’ electronics have improved. It’s now possible for telescopes to stay fixated on a single point, even as the Earth rotates.
More sophisticated technologies make it easier to track the International Space Station, so the crowd knows when and where to scan the skies if it flies by.
Because of the ease and power of digital photography, increasing numbers of astronomers are also bringing cameras.
In the wee hours of the morning, after all the visitors have wandered back to their sleeping bags and campfires, some astronomers stay awake at Glacier Point’s amphitheater to capture far-off digital images.
“I never fail to be thrilled by it,” said Jim Van Nuland of San Jose, 79, a retired IBM computer programmer who for decades has helped organize the San Jose Astronomy Club’s trip.
“I can do this for people,” he said. “I can’t sing songs. I can’t dance. I can’t write a poem. But I can run a telescope.”
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