Haleakala National Park will serve as a prime viewing spot as the planet Venus crosses in front of the sun Tuesday.
The rare spectacle - which happens twice in every 243 years - is attracting some astronomers and visitors to Hawaii, the only state from which the six-hour event will be visible from start to finish, according to park officials.
With help from Seabury Hall science students, Haleakala park staff will host visitors wanting to see the phenomenon known as the "transit of Venus" at the park's visitor center and summit building.
The transit of Venus, which occurs when Venus passes between Earth and the sun, is photographed from Hong Kong on June 8, 2004.
The park will have so-called "sunspotter" devices, which project the sun's image onto a piece of paper, allowing as many as 30 people at a time to safely view the event.
The event will take place from about noon to 6:45 p.m., when the planet will appear as a small black dot against the surface of the sun.
"It's cool to see another planet. We don't get to see planets during the daytime," said Jeff Bagshaw, interpretation ranger for the park. "It's little proof of how small we are since Venus is about the size of Earth. It's kind of humbling."
Early scientists used Venus transits to measure the size of the solar system, he said.
"The original idea was if they could collect data from two parts of the world . . . they could triangulate the distance of Earth and Venus to the sun," Bagshaw said.
He said one Big Island tour company has sold 200 tickets to take people partly up the 13,796 foot Mauna Kea for viewing the upcoming event. But Bagshaw noted that the 10,023-foot Haleakala would likely offer a better vantage point because the summit portion of the park is typically above the clouds.
Though the last transit was in 2004, the next won't be until 2117.
Bagshaw said, "Even our children, likely, won't see this happen again."
* Nanea Kalani can be reached at firstname.lastname@example.org.