Tag Archives: full moon

Saturn, Spica and a Pink Moon partial eclipse

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The moon will be only a degree or two southeast of the star Spica tonight. Tomorrow night (April 25) the Full Pink Moon hangs below the planet Saturn. The map shows the sky facing southeast around 10 o’clock local time. Created with Stellarium

The nearly full moon passes just south of Virgo’s brightest star Spica tonight. For sky watchers across a wide swath of South America and Africa, the moon will do better than that by coming up right alongside and then blocking the star from view. When one celestial body cloaks another, it’s called an occultation.

If you live within the slinky-like path, you’ll see the moon cover or occult Spica tonight. The star will graze the  moon’s northern edge for observers along the path’s northern boundary; the moon’s southern edge along the southern boundary. Times shown are Universal Time (Greenwich TIme). Credit: U.S. Navy

Depending on where you live within the occultation path, Spica could disappear for nearly an hour or just graze the edge of the moon, ducking in and out from behind mountain peaks as the moon slowly travels eastward in its orbit.

Click HERE for a more detailed map.

Tomorrow night we’ll enjoy the Full Pink Moon, named after moss pink (a.k.a. ground phlox), an early spring flower of eastern North America. Other names for April’s full moon include Sprouting Grass Moon, Egg Moon and Fish Moon.

Many parts of the country are seeing their first wildflowers of the season. My first was a dandelion that bravely raised its head from a crack in the asphalt in a downtown alley.

With a bit of imagination you can fancy a variety of characters in the full moon’s blotchy face. Top row: old man carrying sticks, a face. Bottom: woman’s face, rabbit, another face.

You can always find the time of moonrise for your town by clicking over to the U.S. Naval Observatory’s Complete Sun and Moon Date for One Day site. As you watch the moon over the next few nights, do you see a face, a rabbit, an old man carrying a load of sticks? Our eyes form these patterns from the moon’s lighter-toned ancient crust called the lunar highlands and the darker lava plains known as the lunar “seas”.

Visibility map of Thursday’s partial lunar eclipse. Credit: Fred Espanek / NASA

The Pink Moon will briefly assume a dimmer countenance for sky watchers in Europe, Africa and Asia when it undergoes a minor partial eclipse tomorrow night. Only 1.5% of the moon will tread into Earth’s dark inner shadow (umbra) during maximum eclipse with the entire event lasting just 27 minutes.

The moon’s path through Earth’s outer shadow (penumbra) and inner umbra during Thursday night’s eclipse. Times are Universal (Greenwich – England Time). At maximum or greatest eclipse, the top of the moon will look shaved off. Click image for more information. Credit: NASA

While lacking the drama of a deeper partial or total eclipse, it should be fun to watch especially in eastern Europe and Africa where It happens during convenient early evening hours. Keen-eyed sky gazers will notice some dimming of the moon even before it dips into the darker umbra as it first passes through the outer penumbral shadow.

The moon first touches the penumbra at 6:03 p.m. Greenwich time and umbra at 7:54. It leaves the umbra at 8:21 p.m. and the penumbra at 10:11.

The next lunar eclipse for North American will be a very minor penumbral one on May 24. That’s it until next year when the Americas and other regions of the world will be treated to a total lunar eclipse on April 15, 2014.

Worms, crows, maple syrup and the moon illusion

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Tonight – and tomorrow night – the Full Worm moon will rise in your neighborhood. Be sure to catch it. Photo: Bob King

The March full moon goes by a variety of names, all appropriate in their own way in this month of seasonal transition. Full Worm Moon. Crow Moon. Sap Moon. Even Crust Moon to describe the icy crust that forms on snow overnight after a day of above freezing temperatures. These were the names given by Indian peoples across the country to tonight’s full moon.

Your calendar may show tomorrow the 27th as the date of full, but since the moon is “fullest” around 4 a.m. Wednesday Central time, it will appear slightly fuller tonight than tomorrow, at least for sky watchers in the western hemisphere.

Most of us won’t be able to tell the difference anyway with our eyes; such subtleties are reserved for binocular and telescope users.

I’ll bet you’ve witnessed the famous moon illusion sometime in your life. When near the horizon, the rising or setting moon looks HUGE compared to when it’s higher up in the sky. Our logical self knows the moon can’t really be bigger. Matter of fact, it’s actually very slightly smaller, since we have to look around the curve of the Earth to see it at moonrise.

How big does the moon look to you when near the horizon? This illustration shows the impression shared by many – the rising moon appears bigger. Illustration: Bob King

If you photograph the moon near moonrise and then again when it’s high up and measure its size, you’ll find there’s no difference in diameter.

Generations of philosophers and scientists at least as far back as Aristotle, who believed it was magnified by the thick air near the horizon, have tried to get to the heart of why we see it so. Our best current explanations to explain this persistent illusion are the “relative size” and “oculomotor micropsia/macropsia” theories.

Relative size is easy to understand and based on the perceived size of an object relative to objects near it. Trees and buildings in the nearby distance and sharing the horizon with the moon make it appear larger in our brains.

When the moon ascends higher and is surrounded by a large expanse of empty sky, it appears smaller. Psychologists call it the Ebbinghaus Illusion and it’s all about context.

An illustration of the Ebbinghaus illusion. The two orange circles are exactly the same size, yet the one on the right appears larger. The left side demonstrates seeing a full moon in large areas of open sky; the other simulates seeing it in the company of many smaller foreground objects. Credit: Wikipedia

Take a look at the illustration above and you’ll see what I mean by context. Assuming the relative size explanation is correct, one could perform an interesting test by comparing the moon’s apparent size in a busy setting with lots of visual cues to one viewed across an empty field or open lake. Would the illusion disappear in the latter?

Now let’s get acquainted with oculomotor micropsia/macropsia. This lovely bit of terminology provides a physical explanation for the illusion and boils down to this:

* When you look at the moon and then momentarily converge your eyes to focus on closer objects in the landscape, the moon will appear smaller (micropsia) than it was before. If you then glance back at the distant moon, your eyeballs straighten out and the moon’s apparent size becomes larger (macropsia).

We’ve all seen the afterimage of a camera flash suspended in front of us after getting our picture taken. If you recall, the afterimage looks large against a wall on the other side of the room, but if you were to hold your hand in front of your face, the ghostly flash would appear small.You can simulate a camera flash by staring at a bright light for a minute in a semi-darkened room and then looking away.

The human eye is our portal to both the real world and one of illusion. Photo: Steve Jurvetson

Consider trying an experiment described by Don McCreedy, professor emeritus of psychology at the University of Wisconsin-Whitewater, when you’re watching the full moon tonight. Cross your eyes by looking at the bridge of your nose while at the same time paying attention to the moon in front of you. While the moon will be blurred, it should look smaller. Then uncross your eyes and stare at the moon – it will immediately look larger.

Scientists are still working on the ultimate explanation for the moon illusion. For now, it appears to be a combination of both the relative size effect and micropia/macropsia. If you really want to dig into the details, you’ll find much to learn at McCreedy’s Moon Illusion Explained site. To find times when the moon rises for you town tonight, click HERE.

Have fun and don’t get your eyes stuck :)

Sheer beauty of a rising moon

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John Pennoyer of Maple Grove, Minn. finds just the right spot at Brighton Beach Monday night Feb. 25,2013 to photograph the full moon rising over Lake Superior. Photo: Bob King

I thought you’d enjoy a couple photos from last night’s moonrise. Here in Duluth, Minn. the hazy air near the horizon made it one of the most colorful I’ve seen. The contrasting blue tints of Lake Superior and its many tiny “ice islands” provided the perfect complement of color and contrast.

The moon a little earlier than the first photo just as it lifted out of the horizon haze. Photo: Bob King

Wide angle view of the moonrise shows the shoreline and gleam path. The moon was higher up in this photo and its color had lightened to yellow. Photo: Bob King

Full Snow Moon blazes tonight on a horizon near you

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The full moon shortly after moonrise shows a striking orange color. The thick, dusty atmosphere we peer through when looking at lower levels of the sky scatter away blue and green light, leaving the moon orange or red. Photo: Bob King

Don’t forget. Tonight’s the Full Snow Moon with moonrise happening around the time of sunset. To find when the moon comes up for your town, go to Complete Sun and Moon Data for One Day and make your selection. For much of the U.S., moonrise will occur shortly after sunset in a bright twilight sky. Bring your cellphone along and snap a few photos that include the moon in a pretty landscape. It’s not hard to do if you catch the moon early before the sky gets dark.

A colorful bullseye corona rings the waxing gibbous moon this past Friday night Feb. 23. Click image to learn how coronas form. Photo: Bob King

The direction of moonrise depends on your latitude, but for much of the U.S. tonight’s snow moon will first appear at the horizon only a little north (left) of the due east point. One of my favorite full moon activities is guessing where it’ll come up. Since I don’t check in advance, sometimes I’m totally wrong. Somehow that makes it even more fun. Either way, there’s nothing like seeing that first blush of orange in the east alerting you to an impending moonrise.

The atmosphere bends each color of white light differently, something that becomes very obvious on a bright object seen near the horizon. Blue is bent the most and tints the moon’s upper rim in the left photo; red the least and colors the bottom rim. When the moon is higher up (right) and viewed through thinner air, the colors merge and disappear. Photo: Bob King

Bring binoculars along, too. That way you can watch the crazy distortions to the lunar disk when it’s lowest in the sky and shining through the thickest air. Sometimes you’ll see its edges ripple or its bottom pinched off. Keep an eye out for a phenomenon called dispersion. This is where the atmosphere acts like a prism and spreads the moon’s light out just enough to fringe its top edge blue-green and its bottom red.

The closer you look at a moonrise, the more amazing things you’ll see.

Cold winter nights perfect for moon pillar watching

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A fat moon pillar sticks out on either side of the moon last night. Jupiter at upper right. Photo: Bob King

Tonight’s Full Cold Moon is aptly named. We’re now firmly footed in winter and the only way to spring is forward by clock and calendar. The actual moment of full moon occurred this morning at 4:21 a.m. (CST), making the lunar visage slightly fuller last night than it will be when darkness falls tonight. December’s moon rides high across the sky since it’s opposite the low winter sun.

Along with the new season come the ice crystals and the wonderful assortment of halos and pillars they form. Sometimes ice phenomena are obvious as when a car approaches your direction at night accompanied by tall beams of light shooting straight up into the air above its headlights. Ice crystals create similar “light pillars” above and below the sun and moon. These range in visibility from subtle to grand.

In what appeared to be a nearly clear, blue sky Wednesday, I happened to walk by a building which blocked the sun’s over-bright disk from view. There above it a fat spike of light extending upward for 20 degrees or more.

Light reflecting from the surfaces of hexagonal plates and “pencil” crystals floating with their broad sides parallel to the ground create a wonderful variety of sun and moon pillars.

Last night I drove home after shooting photos of a basketball game in Hibbing north of Duluth with the moon and radio my only company. Soon enough I noticed something odd about how the light was distributed about the moon, which shone through a thin layer of cloud.

Instead of being surrounded by a glowing aureole of light, feathers of light stuck out directly above and below the moon. Aha! Another light pillar. At the time a very light snow was falling.

Light reflected from the bottoms and tops of plate and column-shaped ice crystals create light pillars above and below the sun and moon. If conditions are right, it even works with streetlights as in the example. Credit: Dr. Keith C. Heidorn, the Weather Doctor

All these macro-scale phenomena can traced to billions micro-sized ice crystals in clouds or even in minute snow crystals. As the hexagonal plate and column-shaped ice crystals drift earthward, they tip and tilt. Upper pillars are formed when light is reflected downward toward our eyes from the bottom side of the plates; lower pillars when light is reflected upward from the topmost crystal faces. The most striking pillars are often seen at sunset when a front is approaching, bringing with it a veil of cirrus clouds in the west.

When crystals are nearly perfectly horizontal, a narrow column results, but when they’re tilted at a variety of angles to the horizontal, pillars spread into broad feathers like the one I saw around the moon.

Sun pillar in a blue sky this past Wednesday afternoon (left). At right is an ice pillar over distant city lights. When ice crystals are perfectly horizontal rather than tilted at various angles, very narrow beams of light form. Photos: Bob King

Other halos, including the more common “ring around the sun” or 22-degree halo, are formed when light refracts through hexagonal, pencil-shaped ice crystals. Rarer smaller halos originate in pyramidal ice crystals.

You’ll always find something interesting happening in the sky by both the smallest and biggest things nature can muster. For more on light pillars and ice halos, head over to The Weather Doctor site.

PS. I had hoped to give you all a sneak preview of 2013 astronomy events but am still waiting for a few pieces of information. Watch this space – it will appear soon!

Need some dazzle in your life? Don’t miss tonight’s Jupiter-moon show

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Jupiter (left), the moon and the Pleiades star cluster (upper right) last night Nov. 27, 2012. I partially hid the moon behind the tree during the exposure to better show the multicolored corona created by passing clouds. Click to learn more about coronas. Photo: Bob King

November’s been a wonderful month for conjunctions (close approaches) of the planets and moon. Tonight’s no exception. Jupiter and the Full Beaver Moon will be little more than one degree apart in the east all night long. I guarantee a lot of dazzle – this pairing is close enough to get the attention of anyone who happens to look up. Be sure to check it out.

The scene facing east around 10 o’clock local time. Jupiter and the full moon will be joined by the bright stars Capella, Betelgeuse and Aldebaran. Maps created with Stellarium

The two will be closest around 5:30 p.m. (CST). Since the moon is full and rises around sunset, you not only have a great opportunity to see how soon you can spot Jupiter after moonrise but also a chance to photograph the pair during twilight with an interesting foreground scene. For Duluth, Minn. the moon comes up at 4:38 p.m. To find the time for your town, just click HERE.

Simulated view of Jupiter and its four brightest moons seen through 10x binoculars or a small telescope tonight around 9 p.m. CST. II = Europa, I = Io, III = Ganymede and IV = Callisto.

If you stay up late, you’ll see the moon slowly slide under the planet as it heads east in its orbit around Earth. Have a scope or binoculars? Take a closer look at Jupiter – all four of its brightest moons will be lined up on either side of the planet.

You should be able to spot Europa and Callisto, the two farthest from the planet, with binoculars. A scope will show all four with ease. Enjoy the show!

Chance for auroras tonight, a bird-watcher’s moon and more

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The “blossom” of material around the sun is a cloud of plasma speeding toward us at 2.2 million mph. It arrives tonight. The picture was taken by the sun-blocking coronagraph on the Solar and Heliospheric Observatory. Credit: NASA/ESA

NOAA space weather experts forecast possible auroras tonight (Sept. 30) and tomorrow night from the arrival of a storm of electrons and protons from the sun. An Earth-directed coronal mass ejection blasted solar plasma in our direction last Thursday evening. Minor to major magnetic storms are likely as is the potential for auroras for the northern U.S. and higher latitudes.

Tonight’s bright moon may pose a problem with glare, but go out anyway to check the northern sky. I’ll post an update this evening if we get lucky.

The harvest moon rises within the blue-gray band of Earth’s shadow during twilight yesterday. Photo: Bob King

50 flybys in 13 minutes. That’s how many birds I saw winging across the full moon through my telescope from 9:13 to 9:27 p.m. last night. Most were very small and every one flew from east to west, crossing the moon’s face in 1-3 seconds. The anticipation of each brief avian appearance reminded me a lot of meteor shower watching. Late August through October is the best time to follow bird migration by moonlight. The period between waxing gibbous through waning gibbous moon is ideal.

Full moon rise is also a perfect time to notice Earth’s shadow. It’s a thick, dusky band spanning the horizon from northeast to southeast that appears around sunset and rises higher as twilight progresses. The pairing of moon and shadow last night was a delicious sight. If good weather holds, you’ll see the two together again tonight.

Amazing little comet 168P/Hergenrother shows a bright nucleus and short tail when this photo was taken on Sept. 16. At left is a small group of galaxies. Credit: Michael Jaeger

Comets have always been the apple of my observing eye. That’s why I wanted to share this beautiful picture taken by Michael Jaeger of Austria of 168P/Hergenrother. Besides, it’s just fun to pronounce the name: HER-gen-ROTH-er. The comet was discovered by American astronomer Carl Hergenrother in 1998 and returns every 7 years. Although its current predicted brightness is 15th magnitude (very faint), Hergenrother’s been considerably brighter the past month.

Recently it experienced an outburst of activity in its icy nucleus and now shines at magnitude 10.4 along the eastern side of the Great Square of Pegasus. An 8-inch or larger telescope will nab it.

I’d share a map showing how to find it if it weren’t for the bright moon nearby. Later next week, when the moon departs, the comet will be easier to see. I’ll post a finder chart then. Hergenrother flies nearest to the sun on Monday Oct. 1 but misses it by a healthy 131 million miles. Closest approach to Earth happened on September 25 at 39 million miles.

Jupiter is visible in the east around 11 p.m. in early October. To its right is the bright star Aldebaran and the V-shaped Hyades Cluster. Photo: Bob King

I’ve noticed that Jupiter rises above the trees in the northeast by 11 o’clock. If you’re out looking for aurora, take a look in that direction. It’s the brightest “star” you’ll see in the evening hours.

Stay up even later (or get up early) and you’ll see the space station make its final round of morning appearances this coming week. Starting October 9 the shiny bird returns to the evening sky. I’ve listed viewing times for the Duluth, Minn. region. To find out when to watch for your town, log in to Heavens Above or type in your zip code at Spaceweather’s Satellite Flyby site.

* Monday Oct. 1 starting at 5:12 a.m. Comes up from the west, waxes into brilliance and then fades when it enters Earth’s shadow near the top of the sky
* Tuesday Oct. 2 at 5:59 a.m. Nice pass below the constellation Orion
* Wednesday Oct. 3 at 5:12 a.m. Brief appearance when it pops of out Earth’s shadow east of Orion
* Thursday Oct. 4 at 5:59 a.m.  brief pass very low in the southern sky

Let the Blue Moon shine your blues away

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Tomorrow night August 31 we’ll have a Blue Moon – the second full moon this month. Photo ilustration: Bob King

Tomorrow night’s the Blue Moon. It won’t actually be blue unless you happen to be near a volcano. Volcanic ash and forest fires can turn the moon blue. The secret? It’s the ash. If all the ash particles are about 1 micron in size (the period at the end of this sentence is 600 microns across), they efficiently scatter away all the warm colors in moonlight, leaving a pale blue orb. I’ve never seen the phenomenon, but much of the planet saw blue moons for months after the eruption of the Indonesian volcano Krakatoa in 1883. Ditto for Mt. St. Helens in 1980 and Mt. Pinatubo in 1991. If you live in western U.S. where forest fires have been rife this summer, perhaps you’ve seen one too many blue moons.

Farmers burning brush caused the sun to appear blue in the photo taken of the pyramids in Egypt on December 14, 2006. Credit: pyramidCam.com

Most of us will never get to see a real blue moon, but the calender version will shine in Pisces Friday night. According to modern folklore, a Blue Moon is the second full moon in a month. We normally get one full moon a month, but every 2 1/2 years there’s room for another to squeeze in.

That’s because the time between full moons is 29.5 days while most months are 30 or 31 days. Since the first full moon of August was on the 1st, there’s enough time left in the month to make room for a second one on the 31st. If the moon were always full at the beginning of each 30 or 31-day month, we’d get 11 Blue Moons a year. Now wouldn’t that be nice. That doesn’t happen because the moon’s not in sync with the calendar – it marches to its own 29.5 day rhythm.

Full moons have acquired a variety of names handed down from past generations. We get our moon names from the various American Indian tribes as well as the early colonists. Two common monikers for the August full moon are the Sturgeon and Red Moons. The first refers to August being a great time to catch sturgeon and the second to the color of the moon when it rises during the hazy summer months. According to the Old Farmer’s Almanac, the first full moon of August was the Sturgeon and the second, the Red Moon. It’s a fun coincidence that this month’s Red Moon is also Blue.

Full Moon, 1919 by Swiss painter Paul Klee

The term Blue Moon goes back hundreds of years, but it had a different meaning then of “impossible” or “absurd”. The term later morphed into a reference for something uncommon or that rarely occurred.

There are normally 3 full moons in each of the four seasons for a total of 12 per year. In the early 1930s, the Maine Farmers’ Almanac (unrelated to the Old Farmer’s) named the 3rd full moon in a season that had an extra 4th full moon a blue moon.  It’s unclear where the term ‘blue’ came from, but it’s possible it refers to that earlier meaning – an event that rarely happens.

Then in the March 1946 issue of Sky & Telescope magazine, American amateur astronomer James Hugh Pruett wrote an article titled “Once in a Blue Moon”. He either misread the Maine almanac’s definition or interpreted the meaning of “blue moon” differently, calling it the second full moon in a month. Sky and Telescope later adopted Pruett’s definition.

The Blue Moon snowballed into popular culture when Deborah Byrd, host of National Public Radio’s Star Date program,  used Pruett’s definition during a broadcast on January 31, 1980. Word got around and now you know the rest of the story. Fascinating, isn’t it, that the current Blue Moon definition is based on one person’s (mis) interpretation of an earlier definition. Makes you wonder what other accepted “facts” are based on odd turns of events and errors in interpretation.

Last night’s moon lit up the southern sky around midnight. Photo: Bob King

I personally like the modern definition. It still catches the gist of the old almanac sense in a way that’s easy to remember.  The next Blue Moon for North America will be in July 2015. Even better, there will be two blue moons in 2018 – one in January and one in March with no full moon at all in February! The last time that happened was in 1999. For more details on how the current view of blue moons came to be, click HERE to read a complete account of the story by the writers at Sky and Telescope.

I’m looking forward to a  fine moonlit walk Friday night and wish you the same.

Full Thunder Moon goes boom-boom tonight

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Tonight’s the full Strawberry Moon. Pick a place with a wide open view to the southeast to watch it rise around sunset in the southeast. Photo: Bob King

Tonight the Full Thunder Moon (also called the Full Buck Moon) will rise around sunset in the southeast in the constellation Sagittarius. In Duluth watch for it to breach the horizon at 8:55 p.m. For moonrise times for your town, click HERE and add an hour for daylight saving time.

Early summer is when velvety antlers grow from the foreheads of buck deer, hence the traditional name. July’s full moon is also known as the Full Thunder Moon, since thunderstorms are common this month. One blasted through my town only last night.

Like the sun, the moon is colored a deep orange when rising or setting. That’s because we see we look horizontally through the thickest (lowest) part of the atmosphere at those times. The shorter wavelength greens, blues and purples are scattered away by the dense air leaving the yellows, oranges and reds to shine through.

The moon takes on a rich orange color near moonset last week. Our atmosphere acts to remove the shorter wavelengths of light (blues and greens), but the longer-wavelength red rays are able to penetrate the air to your eye. Photo: Bob King

All full moons are directly opposite the sun in the sky. Since the sun’s highest in the summer, the full moon occupies the place directly opposite that spot in the lowest part of the sky. The sun will occupy the spot the moon is in tonight later come this December.

For sky watchers living at mid-northern latitudes, the low-riding moon remains orange to yellow hued for much of the night, since it never climbs high enough to be seen through the thinner air overhead. That’s OK by me. I’ve always enjoyed seeing the yellow moons of June and July. The color is a perfect fit for the warmest season of the year.

Watch out! Here comes May’s super duper full moon

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This weekend's full moon will be the biggest of the year. If you catch it around rising time, the thickness of the atmosphere at low elevation will distort the moon's shape and color it orange. Photo: Bob King

Flower Moon. Super Moon. Call it what you like, May’s full moon is coming to a sky near you this Saturday night. I like Flower Moon, the traditional name, because of its obvious seasonal connection and my own love of wildflowers. On Monday this week the marsh marigolds flashed their yellow blossoms along the edges of our many creeks here in Duluth, Minn. While not the first flower, they’re one of spring’s showiest.

The moon's orbit around the Earth is a flattened circle or ellipse. As it revolves, its distance and speed change continuously over time. The near point, called perigee, happens this weekend. Illustration: Bob King

We get a full moon a month, rarely two, but this one’s special. Full moons vary in size because the moon’s orbit around Earth isn’t a circle but an ellipse, a sort of flattened circle with Earth a little off to one side. As the moon revolves around our planet, it’s distance varies from about 222,000 miles to 252,000 miles. When closest to Earth, the moon’s at perigee (PEAR-up-gee), and when farthest, apogee (AP-uh-gee).

Because the degree of flatness of the moon’s orbit varies slightly over the year, each month’s perigee and apogee distances vary too. The closest perigee of 2012 will be this weekend, the farthest perigee occurred on January 17.

As the moon’s distance varies, so does its size. A perigee moon is 14 percent larger than an apogee moon. Every month the passes through these points in its orbit, sometimes as a crescent or a half, but occasionally when it’s full. No one particularly cares if the moon’s at perigee when it’s a 5-day-old crescent. When it’s full, we pay attention because, well … full moons are big, bright and round, and we love ‘em.

Seen side by side, the difference in perigee and apogee moons is obvious. Click image to find lunar apogees and perigees for any month. Credit: Tom Ruen

Saturday night and early Sunday morning the moon happens to be at perigee at the same time it’s full, an event that happens a little more than once a year.

Not only will the Flower Moon be the closest full moon of 2012 but it will shine 30 percent brighter than a typical full moon. The question is – will you notice the extra brightness and size of this “super moon”? Maybe if you have a photographic memory, but what you really need a side-by-side comparison with an apogee full moon. Unfortunately we have but one full moon.

The moon this Saturday evening around 10 o'clock local time. Saturn and Spica will lie "two fists" to its upper right. Created with Stellarium

For the adventurous, it’s still worth a try. You can compare Saturday’s moon with the size of something fixed in your environment, say the width of a power pole or the peak of your roof. Note exactly where you’re standing when you make the observation and then return to the same spot on November 27-28 this year when the full moon will be at apogee.

The tighter the fit the moon makes with your marker, the better the chance you’ll see the change in size with your very own eyes.

A caliper with a digital readout might be an ideal tool for measuring the size of the moon.

Ideally you’d want to erect some kind of post with a circular disk on top. That way you could sight the moon any time of year in any part of the sky.

Another idea would be to use a caliper carefully held at a precise arm’s length. A friend could adjust the jaws until the moon just fit between them. You could either leave the caliper locked or record the width and then compare it to the new width measured in November at apogee. I’d love to hear if anyone attempts either one of these methods or uses another of their own devising.

As the nearest celestial body to Earth, the moon has a significant gravitational effect on our planet, raising tides in both the planet’s crust and its oceans. Tides are strongest when the moon and sun line up with Earth at new moon and full moon . The two bodies work together to give us a double tug. Though the sun is fabulously larger and weightier than the moon, its tidal influence is only half as strong.

When the moon and sun line up with Earth, the planet has high tides called spring tides. When the moon is in first quarter phase, the gravity of sun and moon partially cancel each other out, creating low or neap tides. Credit: NOAA

As you might guess, Saturday’s extra-close moon means higher tides than normal, but don’t expect anything terribly dramatic. In most places it will amount to an extra inch with a maximum of six inches depending on local geography.

Can you see the faces in the moon? This weekend will be a perfect time to test your powers of perception.

I encourage you to go out for the fun of watching a big moon rise in the east. We’re all familiar with how much larger the moon appears when near the horizon, an optical illusion based on how we perceive objects near the horizon versus overhead. This moon will of course be even bigger. For the Duluth area, it rises at 8:19 p.m. Saturday just five minutes before sunset. Click HERE, select your state or country, key in your town to get your own personal moonrise time.

For even more fun, see if you can make out some of the interesting patterns in the moon’s face seen by generations of people before us. The dark spots are ancient, lava-filled impact basins called lunar seas or maria (MAH-ree-uh). The lighter regions are the crater-saturated lunar highlands. I’ve included the rabbit, the woman and the familiar man-in-the-moon for your eyes and imaginations. Enjoy the moonlight!