Solar flares and gobs of spots make for fiery fall finale

A freckle-faced Sun earlier this morning December 17 photographed by the Solar Dynamics Observatory. Regions 2242 and 2241 have produced several impressive M-class moderate flares in the past couple days. 2242 has a complex beta-gamma-delta magnetic field ripe for the production of strong flares. Credit: NASA

The Sun cares not for Earth’s seasons. It follows its own cycle of high and low activity. So while winter will soon be underway in the northern hemisphere, things have been heating up in recent days on our home star.

An M8 flare (almost an X-class!) in Region 2242 shines brilliantly in ultraviolet light in this photo taken by the Solar Dynamics Observatory at 10:57 p.m. (CST) last night. Credit: NASA

Nine sunspot groups speckle the Sun today with two of them – regions 2241 and 2242 – still growing and harboring the potential for M-class (moderate) or stronger flares in the coming days. Region 2242 let loose with an M1 flare around 7 p.m. (CST) yesterday evening and a stronger M8 flare at 11 p.m.

Along with so many other spot groups now pocking the solar disk, this week will be a good one for anyone with a small telescope and safe solar filter to get a great view of the Sun. This morning I could easily see Regions 2241 and 2242 with the naked eye through a #14 welder’s glass.

Tongue of fire! A coronal mass ejection (CME) of high speed electrons and protons departs the Sun around 2:30 a.m. (CST) today in the wake of last night’s M8 flare. This photo was taken with a coronagraph that blocks the brilliant solar disk so we can see what’s happening near the Sun. Arrow shows the direction of the blast. Credit: NASA/ESA

The more powerful of the two flares launched a large coronal mass ejection in a mostly southernly direction just below the Sun-Earth plane. However, there’s a chance for some spillover in our direction as particles traveling at over 400 miles per second (650 km/sec) arrive on or about Sunday the 21st, the first day of winter.

Quiet conditions in Earth’s ever-dynamic magnetic environment will be the rule the next couple days, but we’ll be keeping our eyes on those big sunspot groups and a possible glancing blow from that CME. A colorful red and green aurora would be so fitting for the season!

Ophiuchians, it’s time to fight for your sign

The Sun enters Ophiuchus today. A part of this large constellation lies between the traditional zodiac constellations Scorpius and Sagittarius. I’ve outlined its official border, set in 1930, in red. Stellarium

If you were born between November 29th and December 17th you’re being sold a zodiacal bill of goods. The astrology columns will tell you you’re a Sagittarius. Don’t believe it. You’re an Ophiuchian!

Ophiuchus (oh-fee-YOO-cuss) the Serpent Bearer represents a man with the snake Serpens coiled around his shoulders. To the ancient Greeks he was the god of medicine; the snake represented healing because of its seemingly magical ability to shed its skin as if being reborn.

Constellation boundaries before 1930 were often vague and varied from atlas to atlas. Now they’re precisely mapped with borders like those separating one country from another. Credit: Urania’s Mirror

Before 1930, the Sun passed seamlessly from Scorpius to Sagittarius during its yearly trip through the zodiac constellations. Now it spends 20 days in Ophiuchus between the two. In 1925, Eugene Delporte of the Royal Observatory of Brussels proposed the need for clear, universally-accepted constellation boundaries to the International Astronomical Union (IAU).

Boundaries were vague at the time and depended upon the star atlas you were using. Understandably, this created confusion for astronomers about what was where in the sky. If you discovered a new nova, you needed to let others know if it was in Sagittarius, Scorpius or wherever. Delporte drew up boundaries along existing vertical lines of right ascension (similar to longitude but applied to the sky) and horizontal lines of declination (latitude), extending the realm of Ophiuchus between Scorpius and Sagittarius.

Now the Sun can’t help but cross into Ophiuchus on November 29th. It doesn’t depart and enter Sagittarius until December 19th. A genuine zodiac constellation if I ever saw one, but will it ever get recognized as such? That’s up to Ophiuchians. Fight for your zodiacal rights!

Now let’s go a little further and examine the 12 traditional zodiacal signs.

The 12 traditional zodiac signs are the constellations the Sun appears to pass through during Earth’s yearly orbit around our star. Astrology allots an even one month per constellation. The actual time the Sun spends in each varies according to the size of the constellation.

Your astrological sign is determined by which of the 12 constellations the sun was in on the date of your birth 2,000 years ago. 2,000 years ago? Back when Rome was a world power, the Sun really did pass through Sagittarius from late November to late December. Not anymore. Because of something called precession, it occupies that constellation from December 17th to January 20th. All the other signs are likewise off about a month. So if you’re a Leo like I am, you’re really a Cancer in the 21st century.

Precession is the slow wobble of Earth’s axis over a period of 26,000 years caused by the combined gravitational tugging of the Sun and Moon. Spin a top and watch as it slow down. You’ll notice that the axis of the top describes a little circle (wobble) in the air before eventually tipping over. The Earth’s axis describes a similar circle in the sky. Since the pole star is determined by where our axis points, it follows that the pole star will shift position and change over that long cycle. Right now, Polaris in the Little Dipper sits in the hallowed spot at which our axis points, but in 14,000 A.D., brilliant Vega will occupy the position. Due to the cyclic nature of precession, Polaris will return as the North Star again in 28,000 A.D.

The slow, cyclic wobble of Earth’s axis called precession resembles the motion of a top slowing down. The wobble causes the pole star to change and the Sun to move westward along the zodiac. Credit: Earth and Planetary Magnetism Group ETH-Zurich

The Earth’s wobble also causes the sun to drift westward along the zodiac 1.4 degrees (about three sun diameters or an index finger held at arm’s length) per century. In 2,000 years, that adds up to 28 degrees or about one zodiac constellation width. Astrology practitioners stick with the Sun’s position two millennia ago, causing a disconnect between the Sun’s true position and one’s birth sign.

I’m no believer in astrology, but I think I understand why the practice hasn’t updated astrological signs to current times. Precession never stops. In another 500 years, the Sun’s position vs. the signs will have drifted even farther. It makes sense to adopt one time and stick with it. 2,000 years ago is as good as any.

If you’d like to know what your sign should be now in the 21st century, here’s an update:

Sagittarius: Dec. 17-Jan. 20. Capricornus: Jan. 20-Feb. 16. Aquarius: Feb. 16-March 11. Pisces: March 11-April 18. Aries: April 18-May 13. Taurus: May 13-June 21. Gemini: June 21-July 20. Cancer: July 20-Aug. 10. Leo: Aug. 10-Sept. 16. Virgo: Sept. 16-Oct. 30. Libra: Oct. 30-Nov. 23. Scorpius: Nov. 23-29. Ophiuchus: Nov. 29-Dec. 17

Sun keeps close company with the planets / New color maps of Saturn’s moons

Although not an official conjunction, three planets and the Moon are grouped within about 10 degrees of the Sun today. Except for the Moon, which will move on into the evening sky, the planets will be near the Sun the next few days. Stellarium

Hidden by sunlight today, the New Moon and three planets parade across the sky in the constellations Libra and Scorpius. It’s a big celestial gathering and one of the reasons few planets are visible in the evening sky this month — they’re all too close to the Sun.

Hanging like a dewdrop from a blade of grass, Saturn’s moon Tethys (TEE-thiss) is about 660 miles (1062 km) across and made of mostly ice. The narrow F-ring and wider A-ring cross in front of the moon in this image released last month and taken by the Cassini spacecraft. Credit: NASA/JPL-Caltech/Space Science Institute

Mars escapes the glare and so does Jupiter, which comes up in the east like a spark yellow fire around 11 o’clock. Saturn, east of the Sun, is now in the morning sky though still lost in the solar glare. Let’s stop by that planet and its largest moons today and look at some brand new maps made with NASA’s Cassini orbiter.

Color map of Enceladus. The yellow and magenta colors show differences in the depth of surface deposits. The blue “tiger stripes” in the southern hemisphere, where the moon vents water vapor and other material as geysers, show brightly in ultraviolet light. Researchers think it might be due to large-grained ice exposures. Credit: NASA/JPL-Caltech/Space Science Institute/Lunar and Planetary Institute

With its rings and butterscotch clouds, few planets rival Saturn for beauty, but its moons are equally fascinating for their strange colors, textures and alien features. NASA recently released a series of global, color mosaics of six of its largest moons based on 10 years of images taken by NASA’s Cassini spacecraft as it orbited the Saturn system. These are the first global color maps of these moons produced from the Cassini data. The colors are broader than what the human eye sees, extending into the ultraviolet and infrared (beyond red) part of the spectrum. They’re also VERY detailed – just click on any of them for a close-up. I’ve included four of the six. To see them all, click HERE.

Iapetus (eye-APP-eh-tuss) looks very strange with one hemisphere bright and icy and the other covered in about a foot of darker material. Iapetus rotates very slowly – once every 79 days. It’s thought that an impact of a darker object long ago coated part of  its surface, causing that area to absorb more sunlight over the long day. More heat meant more ice vaporized which then re-condensed as frost/ice on the moon’s bright side, further concentrating the darker material. This expanded in a positive feedback loop that eventually led to an ever-whitening hemisphere while the other grew blacker. Credit: NASA/JPL-Caltech/Space Science Institute/Lunar and Planetary Institute

On Tethys, scientists think the dark colors of the moon’s trailing hemisphere are due to changes in ice and minerals caused by bombardment from high-speed particles and radiation in Saturn’s powerful magnetic field. The lighter-colored leading hemisphere is coated with icy dust from Saturn’s E-ring, formed from tiny particles ejected from Enceladus’ south polar geysers. The purplish equatorial band gets its color from high-energy electrons in Saturn’s magnetic field slamming into the moon. Credit: NASA/JPL-Caltech/Space Science Institute/Lunar and Planetary Institute

Meet Dione, a 698-mile-wide moon. Its color variations are believed to be caused by the same factors affecting Tethys – radiation and high-speed particles weathering the trailing hemisphere ice and the effects of icy mist spewed by Enceladus on the leading hemisphere. Credit:  NASA/JPL-Caltech/Space Science Institute/Lunar and Planetary Institute 

Awesome Iceland aurora time-lapse and a bear claw sunspot

Joe Capra’s recently released time lapse of aurora over Iceland and Greenland

Nice work! Take a peek at Joe Capra’s recent 10-day shoot of the aurora and you’ll be licking your chops to fly to Greenland on the next available plane. Capra used three Canon 5D Mark III cameras with various Canon lenses to shoot hundreds of individual photos that he later stacked into a video. The reflections on ice and water are spectacular.

A low, green aurora in the northern sky on November 19th sparked by a coronal hole. Credit: Bob King

Here in the northern U.S., the aurora’s been snoozing. Even though gusts of solar wind from a leaky coronal hole have tickled Earth’s magnetic domain the past few nights, conditions have remained below storm level. The aurora’s been a constant but quiet presence like the embers of an overnight fire.

More low aurora simmers in the north last night (Nov. 20) around 11 o’clock. The band of northern lights, called the aurora oval, hovers directly over places like Iceland and Greenland, so people there get to see displays nearly every dark night of the year. It takes coronal holes, flares and other kinds of heightened solar activity to expand the oval so skywatchers in lower latitudes get their chance. Credit: Bob King

Expect the same horizon-hugging aurora for the next couple nights as the hole in the Sun’s magnetic canopy continues to send pinging particles our way.

That giant sunspot that’s made it through a second rotation of the Sun has been nothing but a tease when it come to flares. On its return a week ago, the group possessed the magnetic complexity to unleash powerful X-class flares, but so far, all’s been quiet on the solar front.

Sunspot group 2209 (older 2192) mimics a bear claw in this photo taken on November 19th by French amateur astronomer Philippe Tosi with an 8-inch telescope. Earth shown for size. Click to see more of his amazing high-resolution Sun image. Credit: Philippe Tosi

Flares aside, the region makes a great sight in the telescope. Shaped like a bear claw, the main spot in the group still spans more than three Earths. Philippe’s photo beautifully shows the fiber-like texture of the outer penumbra fringing the darker umbras.

Sunspots are cooler regions on the Sun’s surface – the reason they appear darker – where strong magnetic fields insulate those areas from their hotter surroundings. Notice the rice grain texture of the background. Called granules, each one’s about the size of Texas and represents an individual cell of hot solar gas rising from below like bubbles in a pot of boiling water. At the surface, the gas cools and sinks back down along the tiny, dark channels separating one from another. Re-heated, they rise again.

Will the Full Frosty Moon give you the shivers?

The Full Moon returns to an eastern horizon near you tomorrow evening. Click to find your moonrise time. Credit: Bob King

November’s the last month that still carries a connection to fall. Once December arrives, there’s no going back. Tomorrow at 4:23 p.m. (CST) the Full Beaver or Frosty Moon will rise near sunset and stay up all night.

This month we notice how much higher the Full Moon is than during the summer months. Why is that? Think where the Sun is right now. Have you noticed how much lower in the sky it is compared to June and July?  As our star hunkers down to its winter lair in Sagittarius, the Full Moon, directly opposite the Sun in the sky, moves into Taurus and Gemini. These are the very constellations the Sun occupies during the summer months when it blazes nearly overhead and cooks skin red if we’re not careful.

The Full Moon rises in the northeastern sky near the border of the constellations Cetus and Taurus. Taurus is one of the zodiac constellations and features the famous Pleiades star cluster about a fist to the right of the Moon. Stellarium

You needn’t worry about a moonburn. Although the Moon shines by reflected sunlight, it’s a dusty mirror covered in cobwebs. For all it takes in, our satellite delivers only 12% of the light back. Brilliant to the eye, it’s more than 165,000 times fainter than sunny Sol.

But as the Sun abandons us, Luna comes to the rescue. Despite its wimpy reflectivity, it’s the brightest object in the night sky. Once we allow our eyes to adapt to the dark, the Full Moon provides more than enough light to see our way around, pick out details of the landscape and even sense color. This is especially true now through early spring when the Moon climbs high in the sky where absorption of light by our atmosphere is least.

Clear November nights usually mean frost as the dew point drops below freezing. Don’t be surprised to see tomorrow night’s Full Moon illuminating your lawn as if it were a plush white carpet. Illustration: Bob King

From the countryside I’ve distinguished green leaves, the red of stop signs and other colors though they’re muted and occasionally take some convincing.

The quality of moonlight fascinates. Shadows are summertime short but black and stark. Contrasts are accentuated. A patch of dark behind a rock becomes a lurking animal. There’s just enough light to get around but not enough to provide the information we need to contain our imaginations. But hey, that’s half the fun.

Light passing through the eye’s lens and adjustable iris stimulates rod and cone cells the retina allowing us to see both at day and night.

Our retinas are equipped with two types of cells that respond to light — cones and rods. Cone cells, which are concentrated in the center of our visual field, are very good at color vision and detecting fine detail but only work well in bright light.

Rods are very sensitive to low light but not sensitive to color. We use them for night vision, peripheral vision and detecting fine motion. Because our “high-def” cone cells aren’t active in low light, the rod cells take over. While they’re great in moonlight, our vision lacks the kind of definition provided by the cones. Everything looks grainy at night like pictures shot at high ISO.

Like the other animals with whom we share the planet, we’re creatures of Earth’s day-night cycle; our vision has evolved to accommodate both brilliant sunlight and the tepid light of night.

King-size sunspot slip-slides away

Active Region 2192 will soon pass beyond the western limb to the farside of the Sun. While it’s size has decreased slightly, it still harbors a complex magnetic field and potential for “farewell flare” or two. This photo was taken today October 28th. Credit: NASA/SDO

Big, attention-getting and explosive, sunspot region 2192 will make a final bow before departing for the farside of the Sun in the next couple days. Many of us grabbed a souvenir photo of the giant spot during last week’s partial solar eclipse. Given its size and complexity there’s an excellent chance it will return in mid-November when the Sun carries it around for Act II.

The most recent large flare from Region 2192 was a powerful X2-class on October 27th. This photo shows the view in ultraviolet light from NASA’s Solar Dynamics Observatory. Credit: NASA

Despite shooting off 5 X-class and 12 M-class flares, none of them lofted a coronal mass ejection (CME) toward the Earth, the reason why there have been no significant auroras during its transit. CMEs are enormous clouds of subatomic particles – mostly protons and electrons – that can strongly interact with Earth’s magnetic field to do everything from damaging satellite electronics and poorly protected power grids to producing spectacular displays of northern lights.

Explosive, particle-releasing flares from region 2192 as it rounds the Sun’s western limb can spiral back directly to Earth along the Sun’s magnetic field lines like a curve ball. Credit: Nathan Schwadron, UNH-EOS

But don’t say ‘bye-bye’ to 2192 just yet. According to Dr. Tony Phillips at Spaceweather, the western limb of the Sun is well-connected to Earth. Should the giant spot flare in the next couple days, particles could spiral back along the Sun’s magnetic field lines directly our way. There’s hope yet for auroras.

Fleet of foot Mercury appears at dawn

Mercury comes into good view the remainder of October and the first week of November low in the eastern sky during morning twilight. This map shows the sky from the central U.S. (Champaign, Ill. in particular) tomorrow morning October 28 about 40 minutes before sunrise. Also shown is the planet’s orbital path in the sky and the bright star Arcturus, which you can use to help you find the planet. Source: Stellarium

Mercury is the solar system’s hot sports car. Not only is it the smallest planet, but it rips around the Sun once every 88 days, faster than any of the others. That’s 4 revolutions for every one the Earth makes. As you read this, Earth’s toting you around the Sun at 66,600 mph. Mercury’s got the pedal to the metal at nearly106,000 mph.

Now through the early November you have a chance to watch this speed demon in morning twilight. Six times a year the fleet planet reaches greatest elongation from the Sun, when it’s highest above the horizon during twilight and easiest to spot. This season that date is November 1st, but you can look for Mercury anytime now through about Nov. 10th.

Mercury has phases like the Moon because of the changing angle it makes to the Sun as viewed from Earth during its 88-day orbit. The dates show inferior conjunction between Earth and Sun (Oct. 16), greatest western elongation (Nov. 1), superior conjunction (Dec. 8) and greatest eastern elongation (Jan 14) when the planet returns to good evening sky viewing. Credit: Bob King

Unlike the outer planets, which orbit beyond the Earth, Mercury orbits between our planet and the Sun. That’s why it never strays far from the Sun in the sky and only puts in an appearance after sunset at dusk or before sunrise at dawn. Because it’s in such an orbital hurry, we usually only get to see the planet for a couple weeks during each favorable elongation.

Mercury shows phases like the Moon. This is approximately how the planet will appear in the next few mornings. Source: Stellarium

To the eye, Mercury looks like a fairly bright star (magnitude 0 and brightening to -0.7 in the next two weeks), but through a small telescope it shows phases just like the Moon and Venus.

Right now it’s a fat croissant but it will fill out and brighten in the days ahead.

Take advantage of the late morning sunrises in the days before we lose Daylight Saving Time to find Mercury at a reasonable hour (around 6:40-7:15 a.m. from many locations).  Look “one fist” above the eastern horizon about 45 minutes before sunrise.


Moon bites sun, mankind cheers!

The sun sets while still in eclipse as seen from Duluth, Minn. Thursday evening October 23. Credit: Bob King

I hope you all got at least a glimpse at the partial solar eclipse this afternoon. The weather cleared off just in time here for a beautiful view from over Superior Bay in Duluth, Minn. As expected, many of us couldn’t take our eyes off the magnificent sunspot group.

Sometimes clouds can be your friend. Credit: Stuart McDaniel

Although we looked at the eclipse through the telescope and camera back, my friend and I agreed the best views were at 1x magnification using nothing more than mylar and welder’s glass. Both the nibbling moon and sunspots were easy to see, and without a frame around the scene, the Sun felt closer, more natural.  Because we watched from an open site on a bay, dappled sunlight on water added a nice touch.

Fr. Larry Regynski’s niece creates pinholes with her hand and uses it to project crescent suns on the wall.  Credit: Fr. Larry Regynski

65% of the Sun was covered for us, and while Sun brightness normally drops off near sunset, there was no question that everything around us looked dimmer than normal with half the Sun gone.

Here are a few photos to enjoy. If you took one you’d like to share, please e-mail it to me at and I’ll put it up on the blog.

Still keeping an eye on possible auroras tonight. Right now, all is quiet, but I suspect that big sunspot group sooner or later will crank up the heat.

Eclipse season is over now – the next of note for the Americas will be a total lunar eclipse on April 4th next year.

This is how the eclipse looked in a small 3.5-inch refracting telescope. Credit: Bob King

Amateur astronomer Mike Sangster holds up a photographic solar filter over the eclipsed sun Thursday. Credit: Bob King

Gorgeous! Dimmed by haze and high clouds, the eclipsed sun sets in the west Thursday evening. Credit: Mike Sangster

Me with my head stuck in a telescope … as usual. To observe and photograph the eclipse I used a 94mm refractor fitted with a photographic solar filter. Most exposures were shot at 1/4000-second at f/14. Credit: Mike Sangster

Sweet sunset shot in Owatonna, Minn. taken with a 210mm telephoto at ISO 100, f/18 and 1/4000-second. Credit: Gary Johnson

Mike Sangster crossed one hand over the over to create small gaps that acted as pinhole projectors. He managed 3 crescent suns on the side of his car. Credit: Bob King

Two crescent suns almost lost in the woods. Left: From Duluth’s Skyline Parkway near Bardon Peak from Art Johnston. Right: From the Pike Lake boat ramp taken by Guy Sander

Biggest sunspot in 5 years may steal the show during today’s eclipse

Active region 2192 (AR 2192) is about the same size as the planet Jupiter or 87,000 miles end to end. This illustration is based on a photo of the  sunspot group taken October 22. Click for more information and animations. Credit: NASA/SDO/Alex Young

Wow, have you ever? Look at that sunspot group. If it seems bigger than any you’ve ever seen you’re right. At least in the last five years. Active region 2192 is the largest sunspot group recorded so far in Solar Cycle 24 which began in 2009. Solar cycles typically last about 11 years and chart the rise and decline of sunspots, flares and other solar activity.

The giant spot group 2192 faces Earth squarely today and should look spectacular during this afternoon’s partial solar eclipse.  Here we see many cooler, darker umbrae surrounded by the lighter penumbrae. The group has a magnetically complex beta-gamma-delta magnetic field ripe for flaring. Credit: NASA/SDO

Yesterday I grabbed my #14 welder’s glass and couldn’t believe how easy it was to see this behemoth. If you have a filter ready for today’s partial solar eclipse, use it to look at the sun anytime, and you’ll see what I mean.

Rarely do naked eye sunspots look like more than dark dots. Region 2192 stands apart. Look carefully through your filter and you’ll discern that the left side (eastern half) looks darker than the western side. That’s because most of the darker bits, called umbrae, are concentrated there.

The sun this morning Oct. 23 with our featured sunspot group facing toward Earth. Credit: NASA/SDO

Sunspots have two parts – a dark core (or cores) called an umbra surrounded by a pale, skirt-like penumbra. Each spot group marks a region on the sun’s fiery outer skin where magnetic energy is concentrated. The magnetic forces that permeate the Sun are the same as those that flow the magnets on your refrigerator but contain vastly more energy because they cover huge regions of the Sun’s surface or photosphere.

Strong magnetic fields within a sunspot group quell the turbulent churning of the photosphere, chilling the region by several thousand degrees. Sunspots appear dark against the Sun’s blazing disk because they’re cooler. If you could rip them away from the Sun and see them alone against the sky, they’d be glaringly bright.

The crazy big sunspot group unleashed an X-class flare around 9 a.m. October 22 seen in these photos taken in two “flavors” or far ultraviolet light by NASA’s Solar Dynamics Observatory. Credit: NASA/SDO

Twisty fields of magnetic energy looping above sunspots can become unstable in the hot, turbulent environment of the Sun’s surface, which bubbles and boils like overcooked oatmeal in a microwave oven, and release their pent-up power in violent explosions called solar flares.

2192 has been no stranger to flares. Harboring a complex beta-gamma-delta magnetic field where the magnetic “north poles” and “south poles” lie side by side, they practically beg to explosively reconnect. Since Monday, the spotted beast has spewed two X-class (most powerful) and 8 M-class (medium strength) flares. So far though, none has been directed toward the Earth.

Watch the big group rotate onto the sun’s face and grow in the 72-hour animation made with NASA’s Solar Dynamics Observatory

That’s likely to change very soon since the group is now squarely facing the planet. Already, NOAA’s space weather forecast calls for a 95% chance for more M-class and 55% chance for X-class flare in the next 24 hours. Space weather is expected to be strong during the same period. That might mean auroras coming around as soon as this evening. I’ll keep you posted.

Not only will the sun be eclipsed this afternoon but the planet Venus shines just 1.1 degrees to its north. Venus is very close to superior conjunction which occurs early Saturday. In the photo, the planet is in the background well behind the Sun. Don’t count on seeing Venus – too much glare! This photo was taken from space by NASA’s Solar and Heliospheric Observatory this afternoon using a coronagraph to block the Sun from view. Credit: NASA/ESA

Good luck with today’s eclipse. If you need more information including viewing times for your city, please see my earlier blog on the topic.

Feel the bliss, don’t miss Thursday’s partial solar eclipse

The solar crescents show how much Sun will be covered at maximum for various locations across the U.S. and Canada during the October 23rd (Thursday) partial solar eclipse. Credit: Jay Anderson

Doing anything Thursday afternoon? Have a few minutes to spareThere’s a partial eclipse of the Sun visible across much of North America and of Mexico you might like to catch. For observers in the U.S. and Canadian West the whole event begins and ends in the afternoon before sunset. Those living east of the Great Plains will see the Sun set while still in eclipse.

During a solar eclipse, the orbiting Moon passes between the Sun and Earth, completely blocking the Sun from view as shown here. In Thursday’s eclipse, the moon will pass a little north of a line connecting the three orbs, leaving a portion of the Sun uncovered. To view a partial solar eclipse, a safe solar filter is necessary. Credit: Wikipedia

Solar eclipses occur when the Moon glides between the Earth and the Sun, temporarily blocking it from view. Total solar eclipses get most of the attention because the Earth- Moon-Sun alignment is perfect. Like a snug lid on a pot, the Moon blanks out the Sun completely to create a dramatic spectacle of a black, fire-rimmed disk set in a plush solar corona.

Partial eclipses happen because the Moon’s orbit is tipped a few degrees to the Sun-Earth line. Most months, it passes north or south of the Sun and misses it completely. But during a partial eclipse, the Moon’s close enough to that line to partially block the Sun from view. Unlike a total eclipse, all phases of a partial eclipse are unsafe to view unless you use a safe solar filter or view it indirectly via projection.

Map showing times and percentage of the Sun covered during Thursday’s partial solar eclipse. Times are Pacific Daylight – add 1 hour for MDT, 2 hours for CDT and 3 hours for EDT. Interpolate between the lines to find your approximate viewing time. The arc marked A shows where the eclipse begins at sunset; B = Maximum eclipse at sunset and C = Eclipse ends at sunset. Credit: NASA, F. Espenak,with additions by Bob King

As you can see from the map, nowhere will this eclipse be total. Maximum coverage will happen in Nunavut Territory in northern Canada where the musk oxen might catch sight of a fat solar crescent 81% covered by the moon at sunset. The farther north you live in the U.S. or Canada, the deeper the eclipse. Northern U.S. states will see around 60% covered compared to 40% in the deep south.

In Duluth, Minn. for example, the eclipse begins at 4:21 p.m., reaches a maximum of about 65% at 5:33 p.m. and continues into sunset at 6:06 p.m. Since the sun will be low in the western sky from many locations, be sure to get a spot with a wide open view in that direction.To find out times and coverage for your city, use these links:

* U.S. Cities
* Cities in Canada and Mexico 

Some of the different kinds of safe solar filters available. They work by reflecting or absorbing most of the light from the Sun, allowing only a fraction through to the eyes. NEVER LOOK DIRECTLY AT THE SUN without one. Click photos for a supplier of eclipse glasses. Credit: Bob King

Solar filters come in a variety of styles from inexpensive eclipse glasses that use an optical polymer to glass welder’s filters to caps you place over the front end of a telescope. It’s important to use the correct kind – don’t stack a bunch of sunglasses and figure “it’ll do” or look through smoked glass. They still allow dangerous UV and infrared light to pass through and will mess up your retinas for life.

Because we’re on the heels of the eclipse, if you don’t already have a pair of eclipse glasses I recommend a #14 welder’s glass. It’s my favorite actually because it’s easy to stuff in a pocket and heavy-duty enough to take a few dings. You can pick one up for a few dollars at a welding supply shop. Only buy a #14 – lower numbers won’t cut it.

A piece of aluminum foil, a pin and a cardboard box are all you need to build a pinhole projector. The tiny hole creates a small image of the eclipsed Sun inside the darkened box which you place over your head. Remember to look at the projection of the sun on the inner wall of the box – not through the pinhole itself.

Projection provides a fine alternative to using a filter. You can mount a pair of binoculars (or small telescope) on a tripod and project the Sun’s image on a sheet of white paper or build your own pinhole projector using the instructions above.

You can mount binoculars on a tripod, cover one lens with a lenscap and project the sun’s image safely onto a sheet of white cardboard. Credit: Bob King

If leaves still cling to your trees this season, the narrow spaces between the leaves act like natural pinholes and will cast multiple images of the eclipsed Sun on the ground below.

You can even place one hand atop the other and let the sun shine through the gaps between your fingers to see the eclipse. Low tech as it gets, but works in a pinch.

Here are some other things to watch for during the eclipse:

* If you live where half or more of the sun will be covered, you may notice a change in the quality of daylight. To my eye, the light becomes “grayer”. What do you see?

* Telescope users will see the mountains and crater rims along the moon’s edge as tiny bumps and projections against the brilliant solar photosphere. You’ll also notice how much blacker moon is compared to sunspots. Guess what? We’ve got a huge sunspot out there right now – Region 2192. Perfect for comparison!

Partially eclipsed sun just before sunset seen from Island Lake north of Duluth in May 2012. Credit: Bob King

*  Those living where parts of the eclipse happen at sunset will get an extra special view of the sun with a big bite out of it right sitting atop the southwestern horizon.

I wish you excellent weather – good luck!