Silhouetted Venus reminder of solar system's size

Astronomers also hosted viewings at Pearl Harbor and Ko Olina. In Maui, 20 couples renewed their vows during a ceremony tied to the transit at the Hyatt Regency Maui, a spokeswoman said.

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."

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.

On the East Coast of the United States, amateur astronomer Vince Sempronio was at a viewing hosted by Montgomery College in Takoma Park, Md., but clouds there — as in many other places — limited visibility of the spectacle. Many at the college viewing crowded around a laptop to watch the NASA webcast instead of the Venus move across the sun.

"I was here at the same spot eight years ago when we had the last transit and I was able to show people, using my telescope then. So I'm not too disappointed," Sempronio said. "If modern science and medicine helps, maybe I'll be around in 105 years to see the next one. But I'm not crossing my fingers."

Oskar Garcia can be reached on Twitter at http://twitter.com/oskargarcia

Contributing to this report are AP Science Writer Alicia Chang in Los Angeles; and Associated Press writers Rachel D'Oro in Anchorage, Kelvin Chan in Hong Kong and Hye Soo Nah in Seoul, Nasr ul Hadi in New Delhi and Noel Waghorn in Takoma Park, Md.