Slideshow: Greatest solar eclipse hits

Roger Ressmeyer / Corbis

See stunning images from past solar eclipses going back to the 1920s.

Launch slideshow

If you can't make it to the South Pacific's eclipse zone in time to watch the sun turn into a "ring of fire" on Thursday, you can still get in on the spectacle online.

The annular solar eclipse begins at 6:30 p.m. ET (22:30 GMT) in western Australia. Over the course of several hours, the moon's shadow will sweep across Australia, Papua New Guinea, the Solomon Islands and the Pacific from east to west, fading into the sunset off the coast of South America.

Because of the relative position of moon, sun and Earth, the moon can't cover the sun's disk completely. For observers who are situated within a strip of Earth's surface that measures 100 to 140 miles (171 to 225 kilometers) wide and thousands of miles long, only the outer edge of the sun will remain uncovered. That's what produces the eerie ring of fire.

The sight will be much like what was visible during last May's annular solar eclipse, and the course of the eclipse will be similar to the Pacific path that was taken by the moon's shadow during last November's total solar eclipse.

If you are in the zone for the ring of fire, be careful: Even that slim ring of sunshine packs enough of a punch to burn your eyes, and you'll need to take precautions. Those precautions can take the form of eclipse-viewing glasses or filters, or pinhole-camera rigs that let you view the eclipse indirectly.

Caution should be the watchword as well for those who can observe the eclipse's partial phase from a wide swath of the Pacific, ranging from New Zealand to Indonesia and Hawaii, as shown in the animation below. NASA's Eclipse website provides further details, including precise time schedules for the eclipse in a variety of locales.

If you're entirely outside the eclipse zone, you won't be so sorely tempted to gaze at the sun. Instead, you can enjoy totally safe views of the eclipse online. Click on the links below for a few of the options:

Slooh Space Camera: Slooh's coverage begins at 5:30 p.m. ET, during the partial phase that leads up to annularity. Slooh's team will provide the commentary for live video feeds from Tennant Creek, Cape Melville National Park and Cairns in Australia. The show also will feature occasional shots of the unsullied sun from Arizona's Prescott Observatory. You can use a Web browser or Slooh's iPad app to tune in.

Coca-Cola Space Science Center: The Georgia-based center will provide a live video feed from Australia's Cape York starting at 5 p.m. ET.

Amateur webcams: Australian skywatcher Gerard Lazarus is gearing up to capture live video of the eclipse, and there may be other on-the-fly feeds. Follow the Twitter hashtag #ASE2013 for updates. 

Television Down Under: The eclipse is likely to make news Down Under, and it's worth checking Sky News Australia and 3News in New Zealand for TV coverage.

If you miss it: Check SpaceWeather.com, Space.com and Universe Today for images of the eclipse after it takes place. You'll also want to keep tabs on Geoff Sims (@beyond_beneath) and Colin Legg (@colinleggphoto) on Twitter.

If you catch it: Got pictures? Please feel free to share 'em with us via NBCNews.com's FirstPerson photo upload page, and we'll pass along a selection of eclipse pics.

More about the eclipse:

• All about the 'ring of fire' eclipse
• Australia to see second solar eclipse in six months
• Flash interactive: What causes a solar eclipse?

Tip o' the Log to Michael Zeiler and Amanda Bauer for eclipse tips.

Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the NBC News Science Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with NBCNews.com's stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

Andrew Wall

Astrophotographer Andrew Wall captured images of the moon before and during the penumbral lunar eclipse (left and right, respectively). "The images were taken from my backyard in Paralowie, South Australia," he said in an email. Six frames were stacked to produce each image.

Did you catch today's eclipse? You probably didn't notice the penumbral lunar eclipse unless you knew it was coming — but fortunately, skywatchers around the world were clearly ready.

This photo by Australian astrophotographer Andrew Wall illustrates just how subtle the eclipse was. Earth's fuzzy shadow dimmed the bright lunar disk at the height of the eclipse, which translated to 9:33 a.m. ET today.

The dimming effect was muted because the moon traveled just through the very edge of the shadow this time around — and not through the deepest part of the shadow, as it did during last December's total lunar eclipse.

The prime viewing area included Australia and the Pacific as well as Alaska and most of Asia.

"There was a very subtle darkening of the lunar limb at totality; barely noticeable to the untrained eye," Pakistani skywatcher Ramiz Qureshi told SpaceWeather.com in a report from Karachi. "In fact, I nearly missed it until a friend reminded me."

Qureshi put together a close-up shot and a wider-angle photograph to create this composite view of the eclipse. We also received a picture from Terry Staats in Chiba City, Japan, via NBC News' FirstPerson photo-uploading page. If you missed today's subtle show, there'll be three replays next year — including a partial lunar eclipse on April 25 and penumbral eclipses on May 25 and Oct. 18.

For more views of today's lunar eclipse, as well as the total solar eclipse that took place two weeks ago, check out SpaceWeather.com's eclipse photo gallery.

Rob Kaufman

Rob Kaufman, an astrophotographer from Bright, Australia, also captured a pre-eclipse picture of the moon at 12:00 GMT Wednesday (left), and a picture at maximum eclipse at 14:34 GMT (right).

Ramiz Qureshi

A composite photo from Ramiz Qureshi in Karachi, Pakistan, shows the slightly dimmed moon above an industrial skyline.

Romeo Ranoco / Reuters

A penumbral eclipse of the moon is seen over Manila in the Philippines. The term "penumbral" refers to the partially shaded outer region of a shadow that an object casts. This type of eclipse occurs when the moon passes through the faint penumbral portion of Earth's shadow.

Terry Staats

Earth's shadow slightly darkens the moon over Chiba City in Japan.

More about lunar eclipses:

• Flash interactive: What causes a lunar eclipse?
• Why a lunar eclipse won't drive you loony
• Nine cool facts about lunar eclipses
• How super was that Supermoon?

Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with Cosmic Log as well as NBCNews.com's other stories about science and space, sign up for the Tech & Science newsletter, delivered via email. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

Hong Kong Observatory

Time-lapse photos show the subtle effect of a penumbral lunar eclipse.

It's no Supermoon, but if you look closely at the right time from the right place, you can see Earth's shadow darken the lunar disk early Wednesday — and even if you're not at the right place, you just might be able to catch the subtle celestial show online.

The penumbral lunar eclipse hits its peak at 9:33 a.m. ET (14:33 GMT), which is too late for the U.S. East Coast: By then, the full moon has set and the sun is up. South America, West Africa and Antarctica are also out of the picture. But most of the rest of the world will see at least part of the eclipse, such as it is. The chart below from NASA's eclipse website shows you what can be seen where, and TimeandDate.com helps you figure out the schedule for your own locale.

Fred Espenak / NASA

The white section of this map indicates where this week's penumbral lunar eclipse will be visible in its entirety. Observers watching from the light gray sections will see only part of the eclipse. No part of the eclipse can be seen from the dark gray section of the map.`

If you're in the eclipse zone, don't expect a spectacle like the total solar eclipse that took place earlier this month — or even like this year's other lunar eclipse, which darkened a piece of the Supermoon in June.

On Wednesday, the moon will pass through the lightest part of the shadow cast by our planet — the penumbra, which lets some sunlight shine through. If you could watch the event from the moon's surface, you'd see Earth cause a partial solar eclipse. The result is that the moon's brightness dims somewhat, but it's not enough to be noticeable unless you know what's coming.

What's more, the moon is at the farthest point of its orbit during this eclipse — about 30,000 miles (50,000 kilometers) farther away than June's Supermoon. The result is that the moon is about 30 percent dimmer than the Supermoon was.

The outlook for watching the eclipse online is dim as well. Slooh Space Camera is prepared to stream a telescopic video view of the moon from Hawaii at 9:15 a.m. ET (14:15 GMT), but the weather at the telescope site is not looking good, Slooh President Patrick Paolucci told me this evening.

"At this point, the penumbral event is in serious jeopardy," Paolucci said in an email. "The event will continue to count down on Slooh, but we may have to pull it tonight. ... We only go live when our feeds are live."

Perhaps the coolest thing about this eclipse is that it demonstrates one of the rules of celestial mechanics: Every time there's a total solar eclipse, you can count on having a lunar eclipse of some sort either two weeks earlier or two weeks later. That's because totality occurs when the sun, moon and Earth are precisely aligned during the moon's new phase — and the moon will still be lined up for an eclipse when it's facing Earth's far side for the full phase. The Inconstant Moon website provides further explanation of the eclipse seasons.

Even if the eclipse webcast is a washout, there'll be more cosmic shows to come: Paolucci says Slooh is planning a real-time video feed featuring Jupiter and its Great Red Spot on Sunday, starting at 8:15 p.m. ET (01:15 GMT Dec. 3). That's the night when Jupiter will be at its closest distance to Earth until the summer of 2021. Slooh's telescopic view is due to come from an observatory on the Canary Islands, accompanied by commentary from Paolucci and astronomer Bob Berman.

After that, stay tuned for the Geminid meteor shower, which peaks on the night of Dec. 13-14. This year's Geminids should make for a super show, because the moon will be in its new phase, leaving the skies clear for the sparkle of up to 100 shooting stars per hour. Factor in a series of space station sightings, and you've got more than enough to make up for a less-than-super lunar eclipse.

More about lunar eclipses:

• Flash interactive: What causes a lunar eclipse?
• Tips for photographing the penumbral eclipse
• Why the lunar eclipse won't cause madness
• Nine cool facts about lunar eclipses
• How super was that Supermoon?

Got eclipse? If you capture a super picture of the less-than-super moon, share it with the rest of us via NBC News' FirstPerson website for user-generated content. We'll publish a selection of images in a follow-up posting on Wednesday.

Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with Cosmic Log as well as NBCNews.com's other stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

The dolphins didn't come out for today's total solar eclipse in the Coral Sea, but hundreds of tourists were on deck to catch our cruise ship's biggest show. And most importantly, the sun came out as well.

That was the whole point behind seeing the eclipse from the Dawn Princess, which has been making stops along Australia's northeast coast for the past week. It may not be the steadiest viewing platform, but an expert navigator can sail to a spot in the narrow track of totality where clouds won't spoil the view.

"This is the real advantage of being on a ship," Patricia Reiff, director of Rice University's Space Institute, told me during today's eclipse extravaganza.

Solar eclipses occur when the moon passes in front of the sun, and the partial phase of today's event could be seen from a wide swath of the Pacific. But the total phase — during which the moon's disk blots out the entire solar disk — is visible only from a strip of Earth's surface measuring thousands of miles in length and less than 100 miles in width. The Dawn Princess' southeast course from Australia's Port Douglas to Sydney was plotted out to put the ship and its nearly 2,000 passengers right in the middle of that track at eclipse time, which was 6:39 a.m. local time on Wednesday (on the Western Pacific side of the International Date Line).

By 4:30 a.m., Reiff and her group from EclipseTours.com staked out a prime spot on the port side of the ship's top deck, near at the stern. This was Reiff's 13th solar eclipse, but it was the first brush with totality for Andrea Pond, one of the tourists in the group. She was sailing on the Dawn Princess along with her husband, Stan, who was an eclipse-chaser long before he married Andrea.

"It's not everyone who wakes up at 4 in the morning to see a two-minute happening," Andrea said.

I was on the cruise with my wife, two of my brothers, my sister and a few friends, but Reiff let me tag along with her group as well. So I was with the other eclipse-chasers at about 5:45 a.m., just after sunrise, when German astronomer Joachim Biefang peered through his solar telescope and cried out "First contact!"

First contact was when the moon's disk began passing over the sun's disk. We had to wear freaky-looking solar-filter glasses to watch the moon slowly chew away at the sun.

Alan Boyle / NBC News

Rice University astronomer Patricia Reiff, at right, helps members of her tour group get ready for the total solar eclipse aboard the Dawn Princess.

Tonia Boyle

Alan Boyle watches the last stages of the sun's disappearance aboard the Dawn Princess.

Alan Boyle / NBC News

A single finger blots out the sun's glare just before the total solar eclipse.

Alan Boyle / NBC News

Tonia Boyle takes in totality during a cruise on the Dawn Princess.

Slideshow: Total solar eclipse seen from Australia

John Brecher / NBC News

Glimpse eye-opening scenes from Wednesday's total solar eclipse in the Southern Hemisphere.

Launch slideshow

The ship's course was nearly perfect: Once the sun climbed above a bank of clouds on the horizon, we had a wide-sky view. "Let's have a little gratitude, everybody," Reiff told her group, which had swelled to a couple of dozen of people in one of the ship's sweetest viewing spots.

Hundreds more staked out their own positions around the top deck. My family was along the rail, near the halfway point on the port side. My brother Steve and his wife, Joan, recalled how a troop of dolphins popped up on the surface during their 1998 eclipse cruise in the Caribbean — and they hoped it would happen this time as well. They speculated that the marine mammals would want to find out the reason for the darkening sea.

We kept looking back behind the ship in case the sea erupted with dolphins, but the sun was the center of attention. As we counted down to totality, we folded our fingers together and held them up to project crescent-shaped images onto the deck. Soon the sun's light faded to an eerie golden shade. "It's like a storm is coming," my sister Donna said.

In the moment before totality, the sun's crescent was transformed into a glowing circlet with a bright flash — the famous "diamond-ring effect." That's when the crowd erupted in a cheer, which was followed by oohs and ahhs as the diamond ring turned into a ghostly coronal ring around the totally blacked-out sun. The sky took on a velvety shade of dark violet, with Venus and the southern stars glittering above us.

I oohed and ahhed along with everyone else, and snapped a couple of fuzzy photographs. But mostly, I just marveled at the eerie sight. I imagined how freaked out ancient observers must have been when the sun disappeared, and how relieved they must have been when it returned.

Before we knew it, another diamond ring flashed, the sea and sky brightened again, and my fellow travelers basked in the afterglow.

"It was perfect," one tourist gushed. "I can die now."

"Let's turn the ship around and do it again," Biefang joked.

"If I were a smoker, I'd have a cigarette," Reiff said with a smile of satisfaction.

"Want to look for dolphins?" my wife, Tonia, asked me.

When we went back to the ship's stern, we didn't find any dolphins. But we did find Brian Verkaart, who had just gotten engaged to his girlfriend, Sue Yee Duong.

"Five years, seven months and 12 days ago we met," Verkaart said. "I caught her checking out my butt."

Alan Boyle / NBC News

Sue Yee Duong shows off the engagement ring she was given by her new fiance, Brian Verkaart. It was her third diamond ring, coming after two views of the total solar eclipse's "diamond-ring effect."

Verkaart, who now has three solar eclipses under his belt, decided that the 14th of November was the perfect day to propose. He explained that he and Duong often exchange text messages that read "143," which is shorthand for "I love you." After the eclipse's second diamond ring, Verkaart turned to her and said something like, "Gee, this is the 14th. It'd be great if there were three diamond rings — and here's that third diamond ring."

That's when he got on his knees, offered her the engagement ring and proposed. Duong was totally surprised, but she said yes. ("At least he had the common sense not to pop the question during totality," my brother Steve said when he heard the story.)

Now my family and most of the other passengers on the Dawn Princess have gotten back into the cruise routine. Reiff and her fellow eclipse-chasers are swapping photos and planning their next cruise to totality. Verkaart is faced with the challenge of figuring out how to top his diamond-ring surprise.

And the dolphins?

If they had feet, they'd be kicking themselves right now. They missed a heck of a show.

More about the eclipse:

• PhotoBlog: Why I follow solar eclipses 
• Crowd cheers Pacific solar eclipse
• Next date with totality: 2015
• Video: Nightly News recaps the eclipse
• Flash interactive: How a solar eclipse happens

My cruise on the Dawn Princess continues for a few more days, and then I'll be vacationing in New Zealand for another week. I might have a chance to write a postcard or two while I'm in Middle Earth, but regular postings to Cosmic Log won't resume until Nov. 27.

Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with Cosmic Log as well as NBCNews.com's other stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

Fred Espenak / NASA / GSFC

This map shows the thin track of totality for the Nov. 13-14 total solar eclipse, as well as a grid showing the wide area of the Asia-Pacific region and Antarctica from which a partial eclipse will be visible.

More than 50,000 tourists are expected to converge on Australia for the year's only total solar eclipse on Nov. 13-14 — and I'm one of them. If you're not, don't despair: There'll be ample webcasts of the event, thanks to the magic of the Internet.

Most of the throngs will gather in Australia's northern province of Queensland, "Gateway to the Great Barrier Reef," which is already getting set for the additional crush of visitors.

"The challenge and the opportunity is that it takes place over such a short space of time ... but we're not focused on just the black spot in the sky; it's how we use the opportunity to promote the destination," Tourism Queensland's Jeff Gillies told The Cairns Post. The economic impact could amount to $75 million or more. And that's in Australian dollars.

The psychological impact can be just as stunning, even though totality lasts only a few minutes at most: When the moon fully covers the sun's disk, the skies darken and the delicate glow of the sun's corona becomes visible around that black spot.

Linda Bugbee, a tourist from Virginia who is heading to Australia to see her fourth solar eclipse, told The Associated Press that her first brush with totality "was a lot more emotional than I expected."

"Time sort of stops, but you know it's only going to last a minute or so," she said. "You sort of take the universe and the planets for granted, but when this happens, it seems so real."

It all seems so unreal for me: While Linda Bugbee and her husband will be watching the eclipse from the city of Cairns on Nov. 14, I expect to be looking up from the deck of a cruise ship off Australia's east coast. The Dawn Princess is due to find a clear patch of sky somewhere within the track of totality, which measures roughly 100 miles wide from north to south, and thousands of miles long from east to west.

The eclipse begins at sunrise in Australia's Garig Ganak Barlu National Park, and ends at sunset about 500 miles west of Chile. A partial solar eclipse will be visible across a wider stretch of the Pacific, Australia, New Zealand, Antarctica and South America. This video shows you how the event will develop during the day.

Post-dawn darkness is due to fall on Cairns at 6:39 a.m. AEST on Nov. 14, which translates to 3:39 p.m. ET Nov. 13. You should be able to follow the eclipse online via these webcams:

• University of North Dakota's SEMS team on Ustream.
• Panasonic Eclipse Live plans solar-powered webcast.
• Gorge Creek Orchards in Mareeba in northern Australia.
• Total Solar Eclipse from Brisbane on the Australian coast.
• Total Solar Eclipse from Oak Beach near Cairns.
• Eclipse 2012 promises a webcast that will be carried by NASA.

There'll surely be more webcams available as we get closer to the event. Please feel free to add your favorites in the comment space below. I'll  fill you in on my own brush with totality after the eclipse — but for most of this month, I'll be vacationing Down Under and touring Middle Earth. Regular postings to Cosmic Log won't resume until Nov. 27. In the meantime, turn to NBCNews.com's Science and Space sections to keep on top of the news. G'day, mates!

More resources for eclipses:

• Eclipse-Maps.com
• Newcastle Astronomical Society
• Port Douglas Solar Eclipse 2012
• Destination Cairns by Daniel Fischer
• Wikipedia: Solar eclipse of November 13, 2012
• NASA: Total Solar Eclipse of 2012 November 13

Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with Cosmic Log as well as NBCNews.com's other stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

Submitted by Robin Taylor / UGC

Earth casts a sharp shadow on the moon's disk during the height of Monday's partial lunar eclipse, as seen from Wichita, Kan.

The full moon put on a show today from one side of the Pacific to the other, in the form of a partial lunar eclipse.

Unlike last month's annular solar eclipse, half of the world could see Earth's shadow fall upon the moon's disk at one time. The viewing zone took in most of the Americas, the Pacific, Australia and East Asia. At the time of maximum eclipse, 37 percent of the moon was covered with darkness.

Even if you were in the eclipse zone, you had to be looking up at the right time, under the right conditions. For North Americans, the right time was before sunrise. For example, the picture you see above was taken at around 5:40 a.m. CT by Robin Taylor, and sent in via our FirstPerson sharing website. Taylor also lucked out with the weather: The wispy clouds add an air of mystique without spoiling the view.

Meanwhile, on the other side of the ocean, skywatchers in Indonesia, Japan and other Asian countries turned their eyes and their telescopes to the skies after sunset.

This lunar eclipse took place just two weeks after the solar eclipse, which also gave an advantage to Pacific Rim observers. That's no accident: Lunar eclipses occur when Earth gets exactly between the moon and the sun, and solar eclipses occur when the moon gets exactly between the sun and Earth. Over the past couple of weeks, the tilt of the moon's orbit was favorably aligned with respect to Earth for both configurations.

As a reminder of the annular "Ring of Fire" eclipse, I'm including a shot contributed this week by Dario Infini of Carmel, Ind. Infini's photograph shows a woman standing on a high sand dune in Albuquerque, N.M., at the height of the solar eclipse. "The circumstances of clear weather, relative accessibility and a relatively unobstructed view near the horizon made this a very rare set of photos, potentially once in a lifetime," Infini writes.

And speaking of once-in-a-lifetime opportunities, Tuesday offers the last chance until the year 2117 to witness the transit of Venus across the sun's disk. It's worth seeing — but make sure you see it safely. Your options for precautions range from solar-filter glasses to pinhole projectors to webcast views. Here's a guide to safe observing, and here's a guide to photographing the transit. If you get some great pictures, will you please share them with us? You can use the FirstPerson tool to pass them along. 

Oscar Siagian / AFP - Getty Images

A skywatcher peers through a telescope to look at a partial lunar eclipse in Jakarta on Monday evening. The first partial lunar eclipse of the year provided dramatic scenes across Indonesia and other parts of Asia and the Pacific, with a clear moon visible to many as the event unfolded.

AP

A partial lunar eclipse is seen on Monday through the Sapporo TV Tower in Sapporo, Japan.

Submitted by Dario Infini / UGC

Dario Infini took this picture of a woman standing on a high sand dune in Albuquerque, N.M., framed by the "ring of fire" created by May 20's annular solar eclipse. A solar filter gives a golden tone to the scene.

More views of eclipses:

• May 2012: Your views of the annular solar eclipse
• Panoramic view of the eclipse from a California peak
• Relive the 'Ring of Fire' solar eclipse of May 20
• December 2011: Your views of the total lunar eclipse

Alan Boyle is msnbc.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

Wally Santana / AP

An annular solar eclipse is seen briefly during a break in clouds over Taipei, Taiwan.

The sun, moon and Earth lined up today for a spectacular "Ring of Fire" annular eclipse that sparked social rites as ancient as Stonehenge and as modern as the Twitterverse.

Eclipse fans gathered in locales ranging from Japan's Mount Fuji, to the alien-hunting Allen Telescope Array in California, to the ancient Petroglyph National Monument in New Mexico. But they gathered online as well, to share the wonders of the event via webcasts and chatrooms and Twitter feeds.

"Is it bad that instead of just going outside I'm watching photo updates of the eclipse on Instagram?" one tweeter asked.

• PhotoBlog: Must-see eclipse views from around the world
• Your photos of the eclipse ... it's not too late to share!
• Explore an eclipse panorama from California's Lassen Peak

This event held special significance for American skywatchers: It marked the first time in 18 years that an annular solar eclipse could be seen from the United States. Such eclipses occur when the moon is too far away in its elliptical orbit to cover the sun's disk completely, as seen from Earth. As a result, a little ring of the sun remains visible around the moon's dark disk, even at the height of the eclipse. (The term "annular" comes from "annulus," a Latin word meaning "little ring.")

Centuries ago, priests may have celebrated eclipses at Stonehenge with religious rites. But today, the residents of Redding, Calif., celebrated with barbecue parties. "It's become a very social event," said Tim Young, a physics professor from the University of North Dakota who helped organize an eclipse webcast from Shasta College in Redding.

The event began in Asia, where the edge of the moon's shadow touched down at dawn on Monday (on the other side of the International Date Line). A camera crew atop Mount Fuji battled inclement weather that partially obscured the annular phase, but their live Internet stream still managed to catch a few glimpses through the clouds. More than 275,000 viewers tuned in to the webcast, the project's organizers said.

Eclipse tours were arranged in Japan, China and Taiwan to take skywatchers to the central part of the moon's shadow, where the annular "Ring of Fire" effect was visible. Tokyo residents had a ringside seat, so to speak. "It was a very mysterious sight," Kaori Sasaki, who joined a crowd in downtown Tokyo, told The Associated Press. "I've never seen anything like it." 

The moon's shadow raced eastward at a speed of more than 2,000 miles per hour. The annular phase could be seen only from locations along a roughly 200-mile-wide, 8,500-mile-long track, for just a few minutes in any one location. In contrast, the partial eclipse rose and receded over the course of a couple of hours, and was visible over a much wider swath of the world.

The first hints of the partial eclipse didn't show up on the U.S. West Coast until around 5 p.m. PT (6 p.m. MT, 7 p.m. CT, 8 p.m. ET). The annular phase reached its peak for Americans after 9 p.m. ET, along a line stretching from the Oregon-California coast to around Lubbock, Texas.

Astronomers and amateurs gathered to witness the annular eclipse at the Allen Telescope Array, 70 miles northeast of Redding. Guests walked among the facility's 20-foot-wide radio antennas, which monitor the skies for signals from extraterrestrial civilizations, listened to talks from SETI researchers, and then watched the eclipse through safety glasses or specially designed solar telescopes.

One of the guests, William Phelps, peered intently through his 80mm H-alpha telescope, looking for the first signs of the moon poking into the sun's disk. He's a veteran of 16 previous eclipse-viewing sessions, but he still let out a yelp when he spotted the moon's edge through the telescope.

"Yahoo! That's No. 17!" he cried. Then he let the other guests take their own peeks.

As the moon covered more and more of the sun, the California afternoon seemed to get a bit cooler and dimmer, as if a tinted window had materialized in front of the mountain landscape. The sunbeams filtering through the trees threw crescent-shaped patterns on the ground. At the appointed time, the dark moon was completely ringed by sunlight, and the crescents on the ground turned into tiny O's. A cheer went up from the little crowd.

"God, that's beautiful!" Phelps said. After a few minutes, the moon began its slow exit from the sun's disk. "I'm seeing beads," Phelps reported, referring to the "Baily's Beads" effect that occurs when bits of sunlight leak out through the valleys of the moon. 

Slideshow: Greatest solar eclipse hits

Roger Ressmeyer / Corbis

See stunning images from past solar eclipses going back to the 1920s.

Launch slideshow

Elsewhere, more than 5,000 people gathered at the University of Colorado's Folsom Field in Boulder for a mass eclipse-watching party. "We got several really long, good views, especially right close to sunset," university spokeswoman Erin Frazier told me. A full house attended an eclipse teach-in at Petroglyph National Monument in New Mexico, a sacred site for the Pueblo people and one of the prime viewing spots for the "Ring of Fire."

Would-be watchers heeded the warnings about eye safety, and snapped up thousands upon thousands of eclipse-viewing glasses in the days leading up to the event. The University of Nevada at Reno reported that it sold 17,000 of the glasses at $2 each last week, and had to order 10,000 more. Young said he brought 600 of the special spectacles with him to Redding. His supply quickly dwindled. "It's become a mad grab for resources," he said.

Young, who has been involved in more than a dozen webcasts since 2004, said interest in today's eclipse picked up surprisingly quickly. "Three days ago, it was not that big a deal, but as the news started playing it up, people got excited," he said.

Decades ago, before the rise of sun-watching satellites, eclipses provided the best opportunities for astronomers to learn about the sun's structure — and they're still of scientific interest. This weekend, for example, Williams College astronomer Jay Pasachoff organized an expedition to the Jansky Very Large Array in New Mexico to monitor the sun's radio emissions during the eclipse. But experts say the phenomenon's main appeal nowadays has more to do with the human psyche than with scientific studies.

"This can get people to look up from their little anthill lives, and maybe get a sense of the bigger cosmic cycles that are going on all the time over our heads," said Alan MacRobert, a senior editor at Sky & Telescope magazine.

The eclipse experience can have a long-lasting effect, said Seth Shostak, an astronomer at the California-based SETI Institute who conducted a tutorial at the Allen Telescope Array. "Eclipses are like potato chips, notable for the fact that in all recorded history nobody has eaten only one," he joked. "Be warned."

More about the eclipse:

• Eclipse Day! Your guide to the 'Ring of Fire'
• Get ready to chase the eclipse
• Where and how to see the eclipse
• How to see the eclipse online
• How to safely observe the solar eclipse
• How to photograph the eclipse safely
• World's largest solar eclipse party? Game on!
• Why the 'Ring of Fire' will be a rare sight
• See the solar eclipse at a national park
• Satellite to watch solar eclipse from space
• Five myths about the sun
• Slideshow: Greatest eclipse hits
• Share your eclipse photos with PhotoBlog 

Ready for another "potato chip"? The next sky spectacular is a partial lunar eclipse, visible from Pacific locales on June 4. That'll be followed by a rare transit of Venus on June 5. The year's other big target will be a total solar eclipse, visible from Australia and the Pacific on Nov. 13. Stay tuned for coverage of all those astronomical events.

Alan Boyle is msnbc.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter or adding Cosmic Log's Google+ page to your circle. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for other worlds.

Last updated 11:59 p.m. ET May 20.

It's time to put on your eclipse glasses, prepare your pinhole projectors or scout out a sun-watching website: The first annular solar eclipse to pass through the United States in 18 years is on its way.

The moon will start eating away at the sun's disk around 5 p.m. ET today — although that's early Monday morning in Asia, where the eclipse begins. A wide swath of the world between south China and the American Midwest will see a partial solar eclipse, due to the moon's position between Earth and sun. And along a roughly 200-mile-wide track, skywatchers can witness a "Ring of Fire," in which just a thin ring of the sun's disk remains uncovered. There'll be no total eclipse this time around, because the moon is too far away in orbit to match the sun's apparent size. Nevertheless, it's a sight not to be missed.

Here are seven things you need to know about witnessing the eclipse:

Seeing the big picture: Solar eclipses occur when the moon, sun and Earth line up closely enough for the moon to throw its shadow on earthly locations. Annular eclipses, which create that fiery ring around the moon, are actually rarer than total eclipses because the moon has to be relatively far away in its orbit. Check out this interactive for the graphic details.

Seeing it in Asia: The moon's shadow races eastward across Earth's surface at more than 2,000 mph, starting in China's southern Guangxi Province. Theoretically, the "Ring of Fire" could be visible after 6 p.m. ET over Asian urban centers such as Guangzhou, Hong Kong, Macau, Taipei, Osaka and Tokyo. But for many of those cities, the weather outlook isn't that great: Cloudy skies or even thundershowers are in the forecast.

Seeing it in America: The partial eclipse begins over the U.S. West Coast and Canada around 8 p.m. ET, and even earlier in Alaska. Skywatchers in portions of Oregon, California, Nevada, Utah, Colorado, Arizona, New Mexico and Texas can witness the "Ring of Fire" effect at its peak after 9 p.m. ET. As you go farther east, sunset becomes the limiting factor. The U.S. East Coast, for example, will miss out on all phases of the eclipse. Consult NASA's clickable map to find out what will be visible from your locale. The times are listed as UTC, so subtract five hours for Central Daylight Time, six hours for Mountain Time, and seven hours for Pacific Time. Don't forget to check the weather, too.

Seeing it safely: Experts emphasize that you should never gaze at the sun without appropriate eye protection, even when the solar disk is almost completely blocked by the moon during an annular eclipse. You can look at the sun through specially designed eclipse-viewing glasses, or through welder's glass. Those are in short supply now, but you might still be able to find the right equipment at national parks, science centers and other eclipse hot spots. You can also create a pinhole projector with supplies as simple as a sheet of paper, aluminum foil and a box. Or you can just look at the weird crescent-shaped and ring-shaped patterns created when sunlight streams through the trees. Check out this safety guide for more tips.

Seeing it online: If you're outside the eclipse zone, or if cloudy skies spoil your view, you can still choose from more than a dozen webcasts that are promising to follow the phenomenon. If one webcast isn't working, try another. Here's a list of the webcasts we've come across.

Sharing what you see: If you're a Twitter user, you'll want to use a hashtag like #eclipse, #eclipse2012 or #annulareclipse to let the world know about your sky sighting. And if you snap a great picture of the eclipse, won't you please share it with us, via Twitter or Instagram or Facebook? Flag your submission with the #EclipseMSNBC hashtag. We have an extra special option for DSLR users: Just upload your images using the drag-and-drop feature on this PhotoBlog page. 

Seeing the next sky spectacular: The annular eclipse is a treat, but it's not the end of this year's big sky shows. If you have the right equipment — for example, a telescope or a pair of binoculars equipped with solar filters — you can watch the June 5 transit of Venus. (This will be the last such transit until 2117.) There's a total solar eclipse coming up on Nov. 13 that can be seen from Australia and the Pacific, as well as via the Internet. And in five years, totality will make a huge splash across the United States, for the first time since 1979. Sunday's event will provide good practice for all these coming attractions.  

More about the annular solar eclipse:

• Podcast: All about the eclipse and Venus transit
• Get ready to chase the eclipse
• Where and how to see the eclipse
• How to see the eclipse online
• How to photograph the eclipse safely
• World's largest solar eclipse party? Game on!
• Why the 'Ring of Fire' will be a rare sight
• See the solar eclipse at a national park
• Satellite to watch solar eclipse from space
• Five myths about the sun
• Slideshow: Greatest eclipse hits
• Share your eclipse photos with PhotoBlog 

Alan Boyle is msnbc.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter or adding Cosmic Log's Google+ page to your circle. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for other worlds.

Jeroen Frans

Second Life residents watch a virtual presentation about eclipses on Exploratorium Island, in an image by Jeroen Frans (a.k.a. Frans Charming) of VesuviusGroup.com. The Exploratorium is planning a Second Life teach-in during Sunday's annular solar eclipse.

If the weather cooperates, millions of people can witness Sunday's rare "Ring of Fire" solar eclipse — but what if you're one of the billions who can't? You can still watch the event online.

That's what Alan MacRobert, a senior editor at Sky & Telescope magazine, is planning to do. He's based in the Boston area, where not a bit of the annular solar eclipse will be visible. So MacRobert will be cruising the Internet, looking for a webcast with a stable video stream.

He should have plenty of webcasts to choose from. "There are more popping up as we get closer to the event," he told me.

Sunday's spectacle isn't your garden-variety solar eclipse: Because the moon is farther away from Earth than usual, the angular size of the lunar disk isn't quite wide enough to cover up the sun completely. Thus, at the peak of the eclipse, a thin ring of the sun's bright photosphere will remain exposed around the moon's dark circle.

That's what's known as an annular eclipse, which gets its name from the Latin word for "little ring": annulus. The little ring can be seen from a 200-mile-wide strip of territory, extending from southern China, through Japan, across the North Pacific and over to the U.S. West Coast. From the Oregon-California border, the strip goes across parts of Nevada, Utah, Colorado, Arizona, New Mexico and Texas.

The "Ring of Fire" effect lasts just a few minutes. For about an hour before and after the big event, a partial solar eclipse will darken the sun and then retreat. The partial phase can also be seen to varying degrees from a much wider swath of eastern Asia, the Pacific and North America.

If you're in the eclipse zone, do not gaze at the sun without taking proper precautions. Such precautions can range from eclipse-viewing glasses, to specially designed solar filters, to pinhole projectors. Check out this NASA Web page or this video for the details. Here's a detailed video about eye safety from Eyes on the Sky. (Thanks, @AstronomyDave!)

If you're not in the eclipse zone, you're not alone: The U.S. East Coast, South America, Europe, Africa, Australia and Antarctica will be totally left out. And let's face it: Even if you are in the zone, the weather may not cooperate. That's especially the case for places like Hong Kong and Guangzhou, where millions might miss the annular eclipse due to cloudy skies. "This is monsoon season in south China, so they're going to need quite a bit of luck to have a chance of seeing this one," MacRobert said.

Watching the eclipse via a webcast isn't a sure thing, either. The skies might be clouded over at the camera location. There could be technical difficulties. And even if everything works, the webcast could freeze up if the video server becomes overwhelmed with traffic. That's why MacRobert is planning to play the field, and why you'd be best advised to do the same. Here are a few of the options for Sunday eclipse views over a computer screen or smartphone:

Slooh Space Camera: The Slooh website has organized a series of webcasts from Japan, California, Arizona and New Mexico, accompanied by commentary from Astronomy Magazine columnist Bob Berman and Lucie Green, a BBC commentator and solar researcher at University College London's Mullard Space Science Laboratory. The show gets started at 5:30 p.m. ET Sunday, when the eclipse will be just getting good in Japan. Prime time for the webcasts from the American West will kick in around 8 p.m. ET. For more, check out Slooh's news release.

Eclipse Live from Fujiyama: Panasonic is planning a solar-powered webcast from high atop Japan's Mount Fuji, which is inside the track of annularity. The team will charge up batteries from an array of electricity-generating solar cells at a base camp, then carry the batteries up to the camera site. Video coverage via Ustream is due to start up at 5 p.m. ET. This YouTube video previews the event. For updates, check out the project's Facebook page and Twitter stream.

Hong Kong Observatory: The webcast from Hong Kong is due to begin at 5:41 p.m. ET.

Live-Eclipse: Japanese eclipse-chasers plan to be webcasting via Ustream at 6 p.m. ET. 

More from YokosoNews: This page from the Japanese news site lists lots of webcasts, generally beginning at 5 p.m. ET or later.

More from Ustream: Do a search on "eclipse" and you'll find all sorts of Ustream goodies, from 5 p.m. ET onward. One user is promising a video stream from the northern tip of Taiwan starting at 4:50 p.m. ET.

AstroBob's viewing guide: Duluth photographer Bob King provides a vivid guide to the phases of an annular eclipse and also links to AstronomyLive.com as a potential source of webcasts.

University of North Dakota: UND's SEMS (Sun Earth Moon Systems) team is organizing an eclipse webcast from Shasta College in Redding, Calif. The streaming is due to begin at 8 p.m. ET, and there's a chat window that lets you compare notes with other eclipse fans. The UND team has been doing eclipse webcasts since 2004, so they've built up a loyal following over the years. 

Scotty's Sky: Skywatcher Scotty Degenhardt is promising an unconventional webcast of the annular eclipse via his iPhone from Area 51's "Black Mailbox," a popular gathering place for UFO fans in the Nevada desert. The show is set to start at 8:10 p.m. ET. Check out Degenhardt's website for the details.

Exploratorium in Second Life: Speaking of "unconventional" ... San Francisco's Exploratorium science center is planning to provide information about the eclipse in the Second Life virtual world. If you're a Second Life resident, set a course for Exploratorium Island.

If you're wowed by webcasts, stay tuned: There'll be another big event on June 5, when the planet Venus makes a must-see transit across the sun's disk; and again on Nov. 13, when a total solar eclipse takes place.

Are there any annular eclipse webcasts I'm missing? Pass 'em along in the comment section below.

Update for 12:10 p.m. ET May 18: To find out whether any part of the eclipse will be visible from your locale, consult this clickable map from NASA. The times are listed in UTC. Subtract four hours to convert to ET, five hours for CT, six hours for MT, seven hours for PT.

Correction for 4:50 a.m. ET May 20: I mistakenly placed Shasta College in Whittier, Calif., rather than Redding. That reference has been fixed ... sorry about that.

More about the eclipse:

• Get set to chase an annular eclipse
• Where and how to see the eclipse
• See the solar eclipse at a national park
• How to photograph the eclipse safely
• Interactive: What causes a solar eclipse?

Alan Boyle is msnbc.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.