Have you ever seen the zodiacal light? This huge pearly pyramid is on its best display in the Northern Hemisphere on moonless evenings from February through April. All you need is a location far from artificial lights (at least 40 miles from a small city and 80 miles from a major metropolis) that also has an unobstructed western horizon.

Go out an hour after sunset and look to the west. Even though the Sun is now far below the horizon, a huge dome of light marks the spot where it disappeared. As this light fades and shrinks down to the horizon, another glow will be unmasked; a tall, leftward-slanting pyramid of light. It follows the path of ecliptic, running left of Aries and then between the Hyades and Pleaides, the sky's most spectacular star clusters.

Aside from its shape, you might think it was just part of the twilight, but it will linger long after the rest of the sky is fully dark. The first time I saw the zodiacal light, I thought it was light pollution, but light pollution forms a low band along the horizon. It's amazingly brighter — even brighter than the Milky Way — and once you've seen it, you'll never again have trouble recognizing it.

What are you seeing? The zodiacal light is the combined glow of countless tiny particles (debris from comets and asteroid collisions) that orbit the Sun. See our article Have You Seen the Zodiacal Light? for more information.

Fred Schaaf's Northern Hemisphere's Sky column for June 2010 discusses some phenomena that are visible in twilight, one of them being the Belt of Venus.

Fred simply mentioned the Belt of Venus, but I thought it needed more explanation.So I picked up a phrase from the internet, and described the Belt of Venus as "an arch of pinkish light above the shadow that Earth casts on the atmosphere opposite the sunset." Fred demurred, describing it as "pinkish border to Earth's shadow."

Unfortunately, I had no first-hand experience to fall back on. As an astronomy writer, I knew the term, of course. And reading about it in various sources, it was obvious that I must have seen it dozens or hundreds of times, but I had never recognized it.

Fortunately, it was clear the next few nights, so I was able to observe the Belt of Venus several times in a row, both in the evening and morning. The bottom line is that as usual, both Fred and I are right. It is a border to the shadow, but it also forms a striking arch — though an exceedingly low and broad one.

All you need to see for yourself is a clear evening and a site with an unobstructed eastern horizon. A hilltop, lakefront, or beach is ideal.


Right after the Sun sets, tear your eyes away from the arresting scene in the west, and look east to see a bright pink band opposite the Sun. This is the light of the sunset where you're standing being reflected off the atmosphere some 50 or 100 miles east of you, as shown above.


Three minutes later, the pinkish band has become fainter, but with a richer hue. Surprisingly, it has started to lift off the horizon. Now there's a thin band of bluish sky below the pink.


Six minutes after sunset, the dark blue band below the pink ribbon is beginning to take on shape and substance. It is now clearly rounded, taller in the middle than on the sides.

You are, in fact, seeing Earth's shadow. The Sun is now setting about 100 miles west of you. That light is still reflecting off the atmosphere to your east, but now some of it is blocked by Earth itself — even, just a little, by you standing on that hilltop. So the lowest part of the atmosphere opposite the sunset is no longer lit up.

Fifteen minutes after sunset, the pink has dissipated. But you can still make out Earth's shadow in the east as a huge, low hump of darker sky along the horizon — exactly the opposite of the normal situation, where the sky is brightest along the horizon and darker toward the zenith.

You are watching the onset of night. Soon, Earth's shadow will grow and darken dramatically, and eventually it will cover the entire sky, allowing you to look out at the greater universe that's usually hidden by the Sun.

Why is the Belt of Venus so little known? Partly it's because it's a fairly subtle effect. But even more, though people go out to watch sunsets all the time, they rarely think to turn away from the spectacular vista in the west and see what's happening on the opposite side of the sky.

Clyde Tombaugh discovered Pluto 80 years ago today. Coincidentally, I spent much of last week working on charts to help people locate and observe Pluto in 2010. And just two weeks ago, Kelly Beatty published an article describing new and exciting findings about Pluto. So this planet — or whatever you want to call it — has been on my mind a lot recently.

I've always been perplexed by the people who felt upset when Mike Brown and his team discovered another object both larger and farther from the Sun than Pluto. For people who don't remember, this object was first named 2003 UB₃₁₃, then Xena (after the Warrior Princess), and finallly and most appropriately, Eris, after the goddess of discord.

Ever since the Kuiper Belt was discovered in the 1990s, it's been apparent that Pluto is a member of this family. And it seemed extremely likely even then that it was only a matter of time until some Kuiper Belt object proved to be bigger than Pluto. But this doesn't detract from Tombaugh's discovery at all — quite the contrary!

It was obvious from the moment its orbit was calculated that Pluto was different from the other big planets. It seemed like a dead end, a footnote. Now we know that on the contrary, Tombaugh's discovery was a beginning, not an ending; he was a half century ahead of his time when he found the first KBO.

As for me, Pluto's luster certainly hasn't been diminished, since it's the only Kuiper Belt object that I'll ever see through the eyepiece of my own telescope — unless I someday acquire a monster Dob that's capable of splitting Charon from Pluto or spotting 16.9-magnitude Makemake, as Steve Aggas has done.

It's been several years since I last looked at Pluto. I guess I'll have to take a look this summer, if only as a quality check on my own charts. Pluto is in a unique position now, poised to enter the Small Sagittarius Star Cloud, which is truly crawling with 14th-magnitude stars of comparable brightness. I have no idea whether that will make Pluto harder or easier to spot.

As de facto webmaster for Sky & Telescope, I've been keenly aware of the events unfolding this week in the evening sky. Venus and Jupiter have been approaching an extraordinarily close conjunction, which will take place this evening. Meanwhile, Vesta, the brightest asteroid, is poised to thread the narrow gap between the spectacular double star Gamma Leonis and 4.8-magnitude 40 Leonis.

I knew I had to keep these events prominent on our website, but I didn't expect to see any of them myself, since the weather was forecast to be cloudy. So imagine my surprise when I looked out the window yesterday just before leaving work and saw a completely clear, dark blue sky!

By sheer coincidence, it was 15 minutes after sunset — just when I had been telling people to go out and look for Venus and Jupiter. So I grabbed the 7×35 binoculars that I always keep in my office, ran up to the top of the hill in the park across the street, and started to look. Sure enough, Venus was plainly visible to my unaided eyes, below the thin crescent Moon and a smidge to the left, just as advertised.

I couldn't see Jupiter with my eyes alone, but it was plenty obvious through binoculars — and seeming very far away from Venus. Hard to believe that it would close that gap in just 24 hours!

I went out after supper to look for Vesta. When I set up my telescope, the sky was still completely clear, but by the time Gamma Leonis was high enough to locate, the clouds had moved back in. And tonight it's going to be snowing. So although I've been tracking Vesta every clear night for the last week, I'll miss both of the climax nights when it's closest to Gamma Leonis.

Oh well, there's always another year. Seeing Venus and Jupiter so close together was an unexpected bonus; I can't ask for everything.

If you're lucky enough to have clear skies this evening, try to find a spot with an unobstructed west-southwest horizon and take a look for Venus and Jupiter as soon as the Sun has set. They should make a splendid pair through a small scope at 30× or thereabouts. And the crescent Moon above them is no slouch either.

Then, later in the night, take a look for Vesta. It's easy to see even in the smallest binoculars, and might just be visible naked-eye if your skies are really dark. Especially if you've never knowingly seen an asteroid, this is a chance in a lifetime. With the brightest asteroid of all at its brightest for the year, situated right next to a very prominent star, with yet another bright star to mark the way, you may never again find an asteroid so well placed for easy observation.

Click here for more information on Vesta and how to find it.

Oh, and if you have a telescope, don't forget to take a look at Gamma Leonis. 100× should be ample to split this double star into its bright golden components. In any case, enter a comment below and tell us how you did tonight.

From Earth’s point of view, Mars is unique. It’s the most Earthlike world we know; backyard telescopes can sometimes show polar caps, surface markings, seasonal white clouds, and windblown dust. Mars also behaves uniquely in our sky. It spends most of its time far away as a tiny blob in a telescope, then every 2.1 years it swings much closer for just a few months around opposition.

Moreover, Mars comes almost twice as close at some oppositions than at others (because Mars has a significantly elliptical orbit that is also near Earth’s orbit). The near and far oppositions (“perihelic” and “aphelic”) come and go in a 16-year cycle.

We’re now near the bottom of that cycle. Mars reaches opposition and makes its closest approach to Earth in late January 2010. But it appears only 14.1 arcseconds in diameter at the time. Mars will appear larger than 12″ through the end of February, and larger than 10″ through late March (see the graph on the bottom). That’s pretty small.

And next time around, in March 2012, Mars will be only 13.9″ wide at closest approach. Not until July 2018 will it peak out again, at 24.3″.

But astronomy is all about making the most of very distant, difficult views. And at least Mars will cross the night sky high for Northern Hemisphere observers. It spends the next five months in and near Cancer, at declinations +16° to +23°.

In a good 4-inch or larger telescope on a night of steady air, you may first make out the bright north polar cap. In February or March you may notice the cap shrinking in the Martian northern spring. Dark surface markings may be harder to discern, depending on which side of Mars is facing Earth when you look. Watch also for bright limb hazes, occasional white clouds, and possibly the obscuring bright patch of a dust storm moving from day to day. But don’t expect impressive views. Every bit of what you see will be a hard-won prize.

It’s one thing to detect a vague smudge or two on Mars’s tiny disk. The smudges become much more exciting if you can identify and name them. Use our Mars Profiler to find out the names of the features on the side of Mars that's facing you.

My friends sometimes ask me why so few of my articles appear in Sky & Telescope. I explain that I'm often too busy editing other people's articles to write ones of my own. Moreover, I do write one very important piece of S&T every month: the Sky at a Glance page that appears in the center of the magazine, right before the all-sky chart. This might just be the single most labor-intensive page in the magazine — but it appears without a by-line.

It's particularly challenging to figure out which events to include in the calendar. I don't want to omit anything important, but I also don't want to send readers on wild-goose chases, searching for events that will be difficult to see or boring to watch. I had serious doubts about including the occultation of Antares on the morning of January 11th. Occutations of 1st-magnitude stars are fairly rare, and this one was going to take place over a heavily populated area — including our own office. On the other hand, it was going to occur in broad daylight over most of that area. All of my calculations indicated that it would be visible through a telescope despite the bright blue sky, but in my heart of hearts, I didn't really believe it.

So naturally, when it turned out to be clear that morning, I had to see for myself. I tried to set up a half hour before sunrise, as my own article advised, but due to complicated logistics, it turned out to be more like 20 minutes before sunrise. That turned out to be ample;Antares was still quite prominent through my 70-mm refractor even at a low 16X magnification. So I cranked the power up to 60X, and settled in for the long wait.

I didn't know exactly what to expect, because I was within a couple of mlles of the graze line — the border of the area where the occultation is visible. If my calculations were off by just a few arcseconds, the Moon might miss Antares entirely. And during a graze, the fact that the Moon isn't perfectly round becomes highly significant. A mile-high mountain at the right spot on the Moon's edge can move the graze line on Earth by a mile.

My best data suggested that the occultation would happen at 7:41, almost a half hour after sunrise. And as that time approached, Antares was (contrary to my fears) sitting nice and solid in the eyepiece. Then, at 7:39:45 — long before I expected — the star suddenly winked out. A couple of minutes later (I couldn't time it accurately), Antares re-appeared, presumably as I was looking through a particularly deep valley along the Moon's rim, glowed strongly for a few seconds, and disappeared again. Around 7:43 it appeared yet again, dimmed, brightened, winked a couple of times, and finally started to glow steadily again as the invisible unlit side of the Moon slipped away from it.

I've seen plenty of occultations before, but those were all simple affairs, where the Moon ran head-on over a star or planet. In such cases, the time of disappearance can be predicted to a split-second, and the star stays invisible until it reappears. In this case, I had only a vague idea when the occultation would start, and the brief halftime reappearance was a totally unexpected treat. It was far more exciting than I had expected.

Next time, I'll have my wits about me, and leave my voice recorder running trhoughout the event. That way, I can take scientifically useful readings, and sync the voice recorder to my watch after the whole thing is over. As it is, I have only the vaguest idea when anything happened. With such drama going on, I couldn't very well take time out to look at my watch!

As I wrote in a previous blog, I like to "do" Sue French's Deep-Sky Wonders column whenever possible. A few nights ago, I finally got a chance to start work on the March 2010 column — with a little trepidation.

Figuring out the illustrations for this article gave me a lot a heartache, because I knew I wasn't' got to be able to do it justice. Normally, Sue covers a small chunk of sky, making it relatively easy to cover the whole thing with one or two charts. This time, her targets stretched over more than 25° of sky, and I also wanted to include the "anchor stars" Castor and Pollux, making the coverage area even bigger.

To make matters worse, a number of the targets in this column are pretty faint, needing highly detailed charts for people who plan to locate them by star-hopping. Trying to cover such a large piece of sky at that level of detail would have consumed all the available pages, leaving no space for the text. Plus, it's really helpful to have photographs of some of the objects both as eye candy and also to give you hints what to look for through the eyepiece.

So I compromised, giving detailed coverage to the most challenging targets, but showing the rest just on a small map with stars to 6th magnitude. At the very least, that shows where everything is in the sky. But would it be adequate for star-hopping?

Not for me, it wasn't. The first two targets, Iota and 57 Cancri, are bright double stars, so they were easy. The galaxy NGC 2683 (which, by the way, I see only now I failed to highlight in yellow!) wasn't too hard either. It's right near a charted star, and at magnitude 9.8 it sticks out like a sore thumb in my 12.5-inch scope.

But I failed humiliatingly on the 11.6-magnitude galaxy NGC 2782, which is several degrees from any 6th-magnitude star. I had to revert to my backup charts (the Millennium Star Atlas) to find this little fellow. It wasn't especially subtle once located; I might have seen it on my first try — but I didn't.

I wonder how much all of this matters. A survey I did a couple of years ago indicated that most people who follow Deep-Sky Wonders either use Go To scopes or else use their own charts (printed or software) to star-hop, and don't rely primarily on the charts in the magazine. But after all, I'm a Deep-Sky Wonders reader too, so my opinions count at least a little. And although I do always have backup charts, I find it mighty handy when everything I need is right there in one place, in a format that's easy to hold up to an eyepiece.

What do you think?

A couple of weeks ago, I promised to write more about my ongoing search for double stars.

In the course of my double-star sessions, I've realized that what I really like about astronomy is the chance to be outdoors and interacting with nature. Sure, it's winter now, but there's no weather where I'd rather be inside than out. As for nature, its most visible manifestation at night is stars — I just love them! Some people say that looking at just plain old stars (as opposed to deep-sky objects or planets) is boring, but not me. There's something magical about turning my telescope to the sky and seeing all those pinpricks of light appearing as if out of nowhere; I never get tired of it.

That's probably why I love star-hopping; it gives me the maximum opportunity to interact with the stars, to actually utilize them as a means to an end. And if you want to star-hop to double stars, there's no substitute for the Cambridge Double-Star Atlas. Most star atlases mark doubles in some way, but few actually label them with their names, as the CDSA does.

If those aren't enough, Sissy Haas's book Double Stars for Small Telescopes is a virtually inexhaustible source, with complete data and thumbnail descriptions of more than two thousand multiple-star systems. And then, of course, Sue French's "Deep-Sky Wonders" column in every issue of Sky & Telescope almost always mentions a few double stars, including some offbeat choices that you're not likely to see listed anywhere else. That's the great thing about Sue — she covers all the warhorses, as well she should. But she also comes up with lots of weird, wonderful stars and objects that are completely off the beaten track.

Incidentally, the March issue of Sky & Telescope, which is now on sale, has a great article on double stars in Leo by Australian astronomer Richard Jaworski. And don't forget the amazing collection of double-star sketches found on Jeremy Perez's website.

Astronomy is an unusual hobby; it snares lots of different kinds of people for many different reasons. For me, it was a natural outgrowth of my love of the outdoors. The one activity that I love even more than stargazing is hiking in the mountains. And combining hiking and stargazing is best of all!

Most people who hike in the U.S. Northeast would agree that September is the best time to do so. The oppressive heat and bugs of summer are gone, the chance of rain is low and the chance of snow even lower, yet the days are still reasonably long. So for the last weekend in September, I took Friday off to do a three-day hike that I'd long dreamed of and never attempted. For those who know New Hampshire's White Mountains, I went north up the Bonds, west across South Twin and Garfield, and then south down the Franconia Range. Many geologists believe that the striking horseshoe-shaped ridge that I followed is the remains of an ancient volcanic caldera.

The weather proceeded exactly as forecast. Friday started cloudy and drizzly, then turned crisp, cool, and windy. Saturday was predicted to be perfect hiking weather, which it indeed turned out to be — cloudless skies, crystal-clear air, gentle breezes, and temperatures around 40°F. (That's T-shirt weather when you're doing strenuous hiking.)

I spent Friday night at Guyot Shelter, high up in the mountains and as far from civilization as you can get in New Hampshire. I was eager to rise early for two reasons. I wanted to take advantage of Saturday's weather and hike as far as possible. And since this was first-quarter Moon, the sky would be truly dark before dawn — giving me a great chance to see the zodiacal light. And indeed, when I awoke around 4:30 on Saturday morning, there was the zodiacal light shining between two trees — as fine a view of it as I've had for several years.

Packing up as quietly as I could to avoid wakening my shelter-mates, I hiked up to the main trail and started to cook breakfast before the first sign of dawn. I could only see the narrow strip of sky above the trail, but that was enough! The Milky Way from Cassiopeia to Auriga ran directly overhead, intricately veined with dark lanes, with the Double Cluster blazing in its center. Quite a backdrop for breakfast!

By the time I was actually hiking, the sky was getting light. Shortly afterward, I emerged above treeline on Mount Guyot to the most glorious view imaginable. Orion and Canis Major were still prominent in the south, while Mars, Castor, and Pollux made a perfect arc overhead. But Venus dominated the view, blazing above a magnificent sunrise glow that stretched the entire length of the eastern horizon. I put on my down jacket and mittens and snapped endless pictures as the sky grew brighter and the mountains around took on a rosy hue. In the lowlands to the north, isolated hills rose out of a sea of fog as far as I could see.

I started to hike again, ducked into the trees, and by the time I emerged above treeline again on South Twin, the Sun was well above the horizon.

Saturday was a great day of hiking by any standard — I ended up walking 14 hours though some of the finest scenery in the East, at one of the loveliest times of year. I crossed six mountaintops, each with a wonderful view, each very different from all the others. And I certainly got a good workout! But none of the time that I spent walking during broad daylight came close to the magic of those hours between the first sight of the zodiacal light and the disappearance of the last stars.

A couple of years ago, I wrote a series of blogs comparing big binoculars and small telescopes. The subject has continued to fascinate me ever since, and I'm now planning to write an article about it in Sky & Telescope — tentatively slated for the May 2010 issue.

A couple of weeks ago, when two weekday nights near new Moon were forecast to be clear back-to-back, I took a day off from work to observe some more objects from Deep-Sky Wonders columns and to compare the three instruments shown at right: a pair of Fujinon 16x70 binoculars borrowed from Dennis di Cicco, my 70-mm f/6.9 refractor, and the Orion 4.5-inch Starblast.

I'm still working on the fascinating — though ultimately unanswerable — question of what sized telescope is equivalent to any given pair of telescopes. How good is the brain at combining the light seen through two separate eyes?

Pretty good, it would seem. Across the board, the images through the 16x70 binoculars are clearly superior to my 70-mm telescope at 16X. More surprisingly, I've actually found some cases where the binoculars beat the StarBlast running at 18X, using both higher magnification and much more aperture. In particular, the elusive outer loop of the Orion Nebula — the broad, extremely faint circle of light that stretches from Theta through Iota Orionis — is actually easier to see in the binoculars. Stay tuned for more details.

Sky & Telescope readers often comment how much they enjoy reading Sue French's "Deep-Sky Wonders" column. I certainly agree, but to some extent, that's missing the point. Sue is a good enough writer to make her column entertaining as armchair reading, but its real purpose is to be used outside, at night, by the side of a telescope.

Since I'm Sue's regular editor, I make a point of "doing" her columns whenever I get a chance. Among other things, it lets me make sure that the charts and illustrations that I prepare are adequate for finding the things she talks about. And in any case, it's hard to imagine a better way to spend an hour or two.

I particularly enjoyed the column in the November 2009 issue because of its variety. Sue starts out exploring Pegasus I, a galaxy cluster with a couple of very prominent members (NGC 7619 and 7623) and a whole host of fainter ones. I was pleased that, using my 12.5-inch Dob last Sunday at my semi-dark second home in rural NY, I was able to log at least a strong "maybe" for all the ones listed in the article.

Sue sometimes fails to get the respect that she deserves from hard-core deep-sky observers -- perhaps because she spends so much time with her 4.1-inch refractor, or perhaps because she never goes out of the way to took her own horn. In fact, she generally sees more through her 10-inch scope from her far-from-dark backyard than I can through my 12.5-incher at a considerably darker site. Then again, she probably devotes ten times as much time as I do to observing, so her superior skill is hardly surprising.

After I'd spent more than an hour straining to see the 14th-magnitude galaxies described in the November Deep-Sky Wonders, I got to unwind with a lovely succession of relatvely easy double stars, the magnificent carbon star TX Piscium (which I often view), and a charming asterism that I never would have stumbled on if Sue hadn't mentioned it.

But don't take my word for it. If you own a telescope, why don't you try "doing" Deep-Sky Wonders yourself? Sue almost always lists one or more targets that are easy for novices to enjoy as well at least one target that's bound to be a challenge for even the most experienced observer.

Yesterday I kept daydreaming about Galileo. Exactly 400 years ago, on January 7, 1610, the famous Italian astronomer spied the moons of Jupiter for the first time and, once he realized what he'd seen a few days later, created a revolution in astronomy that reverberates to this day.

Backyard observing has changed tremendously since Galileo's time. Our telescopes are so much better, our ability to appreciate what we see vastly improved. But we're still limited by local circumstances — by the time and place we choose to set up our scopes, and by the light pollution that almost certainly degrades our view.

Fortunately, this weekend you'll have not one but two chances to view the universe with first-rate equipment and modern detectors from pristine, dark-sky sites. The good folks at Astronomers Without Borders (AWB) have teamed up with the Virtual Telescope project and Global Rent-a-Scope to provide a remote-observing experience for those of us lacking good skies or too busy to drag our own scopes outside.

The effort, called Big Dipper to Southern Cross, features robotic scopes in two hemispheres. Using your computer, you'll watch as experienced observers slew from one object to the next and show how they capture the wonders of the night sky. You'll be able to chat with other participants and with the telescope operator. This event builds on a successful remote-observing effort held by AWB last September.

So if you've ever wondered what remote observing was like, here's your big chance to try it, along with like-minded amateurs from around the world, and at no cost! All you have to do is make sure your computer has Adobe's Flash plug-in and then go to the Big Dipper to Southern Cross event website.

The northern-sky tour takes place today, January 8th, from 20:00 to 22:00 Universal Time (3 to 5 p.m. Eastern Standard Time). The southern-sky tour is Sunday, January 10th, from 12:30 to 14:30 UT (7:30 to 9:30 a.m. EST).

Industry stats show that by late December the end-of-the-world disaster flick 2012 had grossed $730 million worldwide. This suggests that lots of you have seen it.

But not me. I've got more important things to worry about than this market-driven piece of trumped-up hysteria. After all, an even more alarming calamity awaits us on New Year's Eve: a full Moon — the second one in December.

I couldn't believe that doomsayers had overlooked this dread portent, so I double-checked my facts. Yep, it's all right there on page 52 of December's Sky & Telescope: full Moons occur on December 2nd at 7:30 Universal Time, and again on the 31st at 19:13 UT. Running the numbers, I calculate that those two events take place 29.488 days apart — amazingly close to the Moon's average synodic month of 29.531 days.

And did I mention that late on December 31st there'll also be a partial lunar eclipse, visible from Europe and Asia? And for all this to occur on the final day of 2009, the end of the dread decade of the 00s, the Uh-ohs? Can this all be mere coincidence?

Seriously, I doubt the world will grind to a halt on New Year's Eve. After all, the circumstances were the same 19 years ago, on December 31, 1990 — and there were no global consequences (apart from the debut of the Sci-Fi Channel on cable television).

In modern usage, the second full Moon in a month has come to be called a "Blue Moon." But it's not! This colorful term is actually a calendrical goof that worked its way into the pages of Sky & Telescope back in March 1946. There author James Hugh Pruett wrote how two full Moons fall in a single month seven times every 19 years. He then stated, "This second in a month, so I interpret it, was called Blue Moon."

Pruett's interpretation might have faded into history and been forgotten, had my old friend Deborah Byrd not picked up on it in January 1980 script for the Star Date radio program. She's since moved on to Earth and Sky and set the record straight. But by then this bit of faux folklore had taken on a life of its own.

It's now clear that "Blue Moon" appeared in a 1937 edition of the Maine Farmer's Almanac to denote an extra full Moon in a given season. You're probably familiar with terms like "Harvest" and "Snow" to describe the full Moons at various times of year. But when a fourth one intrudes in the three-month interval between, say, September's equinox and December's solstice, a gap occurs in this naming scheme. That's why editor Henry Porter Trefethen inserted a Blue Moon (as the third of the four) all those years ago in his almanac.

For the numerologists among you, this month's doubletake is the first since May 2007, and the next won't come until August 2012 (there's that scary date again). As for me, if skies are clear when I'm out celebrating, I'll take a peek at that brilliant orb as it rises over the Boston skyline to see if it's an icy shade of blue. Or maybe I'll just howl.

Although I've seen my share of solar eclipses, I have a soft spot for coverups of the Moon. Maybe it's because lunar eclipses often occur in the dead of night, when I can contemplate the umbra's progress serenely instead of being embedded in a frenzied, sweaty crowd waiting for the Sun's corona to make a fleeting appearance. Or maybe it's because I know that more than half of the globe can enjoy a lunar eclipse along with me.

Whatever the reason, I'm going through a little withdrawal right now. February 2008 marked the third total lunar eclipse within a 12-month span and the last time anyone saw the Moon completely awash with umbral glow. Get this: four lunar eclipses happened during 2009, and three of those were merely penumbral — meaning the Moon skirted Earth's shadow so shallowly that even someone paying close attention likely missed these.

So it was with only modest enthusiasm that I reminded myself about a partial lunar eclipse that would take place on New Year's Eve. The eclipse's midpoint came at 19:23 UT, when a slight umbral nick (amounting to only 8% of the Moon's diameter) covered the southern limb.

Skywatchers in the Eastern Hemisphere had the best seats to view this subtle event, and Web postings from across the Atlantic suggest that many of them enjoyed clear skies for the eclipse. But I missed it, because North America was still awash in daylight at the time. (Besides, it was snowing in Boston at eclipse time.)

One of those who opted to watch instead of (or maybe in addition to) ringing in the new year was Anthony Ayiomamitis. Observing from Athens, Greece, he took a series of images that showed the slow progress of the Moon's bright disk through the bit of umbra that smudged its surface. I like the way this series shows the penumbral shading, which can be notoriously difficult to judge by eye.

I asked Ayiomamitis about the thin, bright rims around some of the images in his sequence — a processing artifact perhaps? "No," he replied. "We had some thin high-level clouds, and I am convinced this is the source of the problem."

In any case, I tip my sequin-spangled New Year's hat to him and to everyone who looked skyward last night to watch more than just celebratory fireworks.

S&T.com's guide to eclipses for the coming year is here. Looking that over, you'll note that a total eclipse of the Moon — the first in nearly three years — is coming on the night of December 20–21, 2010.

Only 354 days to go!

Right now I'm daydreaming of being on the other side of the world — on the tiny island of Malé in the Maldives, to be exact. More than being someplace that's lots warmer and more picturesque than my native Boston is this time of year, tomorrow the 100,000-odd Maléans will, weather permitting, see an unusually long annular (ring) eclipse of the Sun.

In fact, notes eclipse guru Fred Espenak, January 15th's event is the longest annular eclipse until the year 3043. Were I in the right place (in the Indian Ocean midway between Madagascar and Sri Lanka) at the right time (7:06:33 Universal Time), I'd be able to watch the Moon's disk completely engulfed by the Sun for 11 minutes, 8 seconds.

Not much of a long-distance swimmer, I'd certainly settle for Malé, where annularity will be nearly as long (10m 45s). Or I might choose the 6m 53s available from Nairobi, the capital of Kenya, or even Chongqing in China (7m 53s). On paper, at least, I could pick a viewing site anywhere along the where the event's 200-mile-wide, 8,000-mile-long track. This eclipse's exceptionally broad path results from the Moon being relatively distant, two days before reaching the apogee of its orbit, and Earth being relatively close to the Sun, having passed perihelion on January 3rd.

The annular path begins at sunrise over central Africa (at 5:14 UT), then crosses open water until it slices directly between the southern tip of India and northern Sri Lanka (at 7:51 UT). The shadow then makes landfall again in Myanmar (formerly Burma) at 8:33 UT before crossing southern China and concluding at sunset just offshore in the Yellow Sea (8:59 UT).

Most everyone in Africa and Asia will see some degree of partial eclipse. In Calcutta and Beijing, for example, the eclipse will become about 75% complete.

If, like me, you're nowhere near the eclipse path, you can witness it vicariously by logging on to one of several online streams provided by dedicated umbraphiles.

You can also check out this year's other eclipses, including a tempting total solar eclipse in July that crosses bits of French Polynesia and Easter Island.