SEATTLE It's a spectacle that won't repeat for another century the sight of Venus slowly inching across the face of the sun.
For some in Washington state, the weather cleared up just enough Tuesday afternoon to see it.
Venus appeared as a small black dot gliding across the disk of the sun. The entire transit, lasting 6 hours and 40 minutes, was visible from the western Pacific, eastern Asia and eastern Australia starting at just after 3 p.m. PDT.
As with a solar eclipse, you should not look at the sun with your naked eye. Instead, use some type of projection technique or a solar filter. NASA says a No. 14 welder's glass is a good choice. Many astronomy clubs will have solar telescopes set up to observe the event. Here are more safe viewing tips from Sky and Telescope.
People unable to watch the transit live could turn to webcasts by NASA and various observatories:
NASA site: http://www.nasa.gov
NASA's Transit of Venus page: www.nasa.gov/externalflash/venus_transit/index.html
Slooh Space Camera site: http://www.slooh.com Exploratorium site: http://www.exploratorium.edu
Anything silhouetted on the sun looks interesting. Seeing Venus is extremely rare, said astronomer Anthony Cook of the Griffith Observatory.
For astronomers, the transit wasn't just a rare planetary spectacle. It was also one of those events they hoped would spark curiosity about the universe and our place in it.
Sul Ah Chim, a researcher at the Korea Astronomy and Space Science Institute in South Korea, said he hoped people see life from a larger perspective, and not get caught up in their small, everyday problems.
When you think about it from the context of the universe, 105 years is a very short period of time and the Earth is only a small, pale blue spot, he said.
While astronomers used the latest technology to document the transit, American astronaut Don Pettit aboard the International Space Station was planning to take photos of the event and post them online.
Meanwhile, terrestrial stargazers were warned to only look at the celestial event with a properly filtered telescope or cardboard eclipse glasses. If the sun is viewed directly, permanent eye damage could result.
In Los Angeles, throngs jammed Mount Hollywood where the Griffith Observatory rolled out the red carpet for Venus. The last time the city witnessed a Venus transit was 130 years ago in 1882. A 2004 transit was not visible from the western U.S.
Telescopes with special filters were set up next to the lawn and people took turns peering at the sun before and during the transit. Astronomers and volunteers lectured about the rarity of a Venus pass to anyone who would listen.
Minutes before Venus first touched the outer edge of the sun, Sousa's Transit Of Venus March blared through. The crowd turned their attention skyward.
Jamie Jetton took the day off from work to bring her two nephews, 6 and 11, visiting from Arizona to the observatory. Sporting eclipse glasses, it took a little while before they spotted Venus.
I'm still having fun. It's an experience. It's something we'll talk about for the rest of our lives, she said.
Bo Tan, a 32-year-old software engineer took a half day off from work and went with his co-workers to the observatory. He admitted he wasn't an astronomy buff but could not miss this opportunity.
He pointed his eclipse glasses at the sun and steadied his Nikon camera behind it to snap pictures.
It makes you feel like a small speck in the universe, he said.
In Mexico, at least 100 people lined up two hours early to view the event through telescopes or one of the 150 special viewing glasses on hand, officials said. Observation points were also set up at a dozen locations.
Venus, which is extremely hot, is one of Earth's two neighbors and is so close in size to our planet that scientists at times call them near-twins. During the transit, it will appear as a small dot.
This will be the seventh transit visible since German astronomer Johannes Kepler first predicted the phenomenon in the 17th century. Because of the shape and speed of Venus' orbit around the sun and its relationship to Earth's annual trip, transits occur in pairs separated by more than a century.
It's nowhere near as dramatic and awe-inspiring as a total solar eclipse, which sweeps a shadow across the Earth, but there will be six more of those this decade.
In Hawaii, hundreds of tourists and locals passed through an area of Waikiki Beach where the University of Hawaii set up eight telescopes and two large screens showing webcasts of the transit as seen from telescopes at volcanoes on other Hawaiian islands.
But minutes after Venus crossed into the sun's path, clouds rolled overhead and blocked the direct view.
It's always the challenge of being in Hawaii -- are you going to be able to see through the clouds, said Greg Mansker, 49, of Pearl City, as he stood in line at a telescope.
The intermittent clouds didn't stop people from looking up through filters, but it did drive some to crowd the screens instead.
Jenny Kim, 39, of Honolulu, said she told her 11-year-old son the planet's crossing would be the only time he'd get to see the transit in person.
I don't know what the future will be, so I think this will be good for him, Kim said as she snapped photos of the webcast with her smartphone.
Astronomers also planned viewings at Pearl Harbor and Ko Olina.
Some observers at the University of Alaska, Anchorage gathered on a campus rooftop, peering at Venus through special filtered glasses and telescopes.
It's not really spectacular when you're looking at it, Kellen Tyrrell, 13, said. It's just the fact that I'm here seeing it. It's just so cool that I get to experience it.
NASA planned a watch party at its Goddard Visitor Center in Maryland with solar telescopes, Hubble-quality images from its Solar Dynamics Observatory Mission and expert commentary and presentations.
Most people don't tend to gaze at the sun for long periods of time because it's painful and people instinctively look away. But there's the temptation to stare at it during sky shows like solar eclipses or transits of Venus.
The eye has a lens and if you stare at the sun, it concentrates sunlight on the retina and can burn a hole through it. It's similar to when you hold a magnifying glass under the blazing sun and light a piece of paper on fire.
It can take several hours for people to notice problems with their eyes but, by that time, the damage is done and, in some cases, irreversible.
During the 1970 solar eclipse visible from the eastern U.S., 145 burns of the retina were reported, according to the American Academy of Ophthalmology.
