Tag Archives: eclipse

In darkness the moon is reborn

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If we could see the moon today, it would be a very thin crescent only a few degrees from the sun. Tomorrow it’s in new moon phase. Maps created with Stellarium

What’s old today but instantly becomes young again tomorrow? If you guessed the moon, you’re right! Today the moon winds up its current cycle of phases as an exceedingly thin crescent so close to the sun it’s invisible in the solar glare.

The moon’s cycle has always been a metaphor for life. Every month it’s born again as a thin crescent in the western evening sky, grows to a half-pie seven days later and reaches its full power and radiance when full at 14 days. After full, the moon’s radiance declines as its phase wanes to last quarter (21 days) and then to a whiskery crescent at dawn. Before it finally disappears in the sun’s glare, the moon, now 28 days old, reaches the end of its “life” cycle. But only briefly. The very next day, moments after new moon phase, it’s reborn again as an evening crescent.

When we run into troubles in our lives, we might look to the ever-renewing moon for inspiration.

The sky looking west-southwest a half hour after sunset Monday evening Feb. 11, 2013. You might be able to spot dimmer Mars in binoculars.

Tomorrow morning at 2:20 a.m. (CST) the moon will be exactly lined up with the sun and pass through new moon phase. Skywatchers in the western hemisphere won’t see the moon either day because it’s in the same direction as the sun and swamped by glare.

By Monday Feb. 11 however, the moon’s orbital motion will remove it far enough from the sun to be visible during evening twilight.  And there’s a bonus. The crescent will float a few degrees above the planet Mercury.

I’ve removed the atmosphere in this illustration so you can see where the moon is today at noon (CST), tomorrow morning when it reaches new moon phase and tomorrow Feb. 10 at noon. It passes north of the sun, which is in the constellation Capricornus. Notice all the planets in the neighborhood.

If we were to follow the moon today through new moon and into tomorrow, we’d notice it passes well north of the sun. Most of the time, the new moon is either north or south of the sun because its orbit is tipped about 5 degrees relative to Earth’s orbit.

The moon’s tilted orbit causes it to swing north or south (pictured here) of the sun from Earth’s perspective. A couple times a year however it crosses directly in front and a total solar eclipse is visible from somewhere on Earth. Illustration: Bob King

Over the course of its monthly cycle, it bobs up and then down along its tilted orbit. But 2 or 3 times a year, when the moon intersects the plane of Earth’s orbit at the same time as new moon phase, it crosses directly in front of the sun and we see a total solar eclipse. In fact, this is the only time we can see a new moon with the naked eye. It looks exactly like what you’d expect – a blank, black disk scrubbed free of its past life, waiting to begin the next as a tender crescent.

The new moon – black disk – is plainly visible silhouetting the sun during a total solar eclipse. Credit: Luc Viatour

Asteroid 2012 XE54 may be eclipsed during close flyby tonight

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The path of 2012 XE54 (in blue) during tonight’s close flyby.  At minimum distance, it will be about 139,500 miles away. Credit: NASA/JPL

Newly-discovered asteroid 2012 XE54 will fly by Earth tonight only 139,500 miles away or slightly more than half the distance to the moon. The rocky body, estimated at between 50-165 feet across (15-50 meters), was discovered only yesterday and will reach minimum distance tomorrow morning around 4:10 a.m. (CST) as it zips through northern Puppis southwest of Sirius. For a few hours before and after that, the asteroid should be visible in 8-inch and larger telescopes at around 13th magnitude. As with all these small bodies, 2012 XE54 will look like a starlight point of light on the move.

When brightest this evening at around 12.9-13.0 magnitude, the asteroid will be cruising through Orion and Monoceros. Positions are shown each hour starting at 9 p.m. CST. Created with Chris Marriott’s SkyMap software

According to Pasquale Tricarico, research scientist at the Planetary Science Institute, there’s a good chance the asteroid will be partially eclipsed by Earth’s shadow between 7:22 – 8 p.m. (CST), an unusual if obscure event. Amateurs and professionals watching at that time might see a drop in the 2012 XE54′s brightness.

It’s not often we get to see an asteroid eclipse. The first known case happened in 2008 when 2008 TC3 passed into Earth’s shadow for an hour before entering the atmosphere, where it shattered and dropped about 10 lbs. of meteorites over Sudanese desert.

Just so we’re clear, we’ve nothing to fear from tonight’s flyby. The asteroid will pass safely by Earth like so many others have in recent years. The map above gives you a general idea of 2012 XE54′s path across the sky. To create your own detailed map to find it in a telescope, click over to the JPL HORIZONS site. There you can set your location and time interval and then plot the asteroid’s positions on a detailed star map. Or you can input its orbital elements into your star-charting program. To see a very cool animation of the possible eclipse, check out Pasquale Tricarico’s website.

Is NASA hiding something? No, but the Earth is

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Pictures of the sun snapped every 15 minutes by the orbiting Solar Dynamics Observatory. Data appears to be missing from the middle five frames. Credit: NASA

So what’s up with those blank squares? You’re looking at a screen capture of a page of pictures of the sun in photographed in ultraviolet light by NASA’s Solar Dynamics Observatory (SDO). The photos were shot 15 minutes apart starting Wednesday evening into Thursday morning this week.

Since SDO circles Earth in a geosynchronous orbit about 22,000 miles high, it “sees” the sun continuously both day and night from a vantage point high above Mexico and the Pacific Ocean. About 1.5 terabytes of solar data or the equivalent of half a million songs from iTunes are downloaded to antennas in White Sands, New Mexico every day. The space station, which orbits much closer to Earth, would make a poor solar observatory since Earth blocks the sun for half of every 90 minute orbit.

SDO’s eclipse season started around 1 a.m. September 6 when the observatory shot a photo of the Earth (top middle) cutting across the sun. Credit: NASA

Did I say SDO watches the sun continuously? Well, not quite. Twice a year for a period of about three weeks around the equinoxes, the Earth gets in the way of the sun from the space craft’s point of view, causing a total solar eclipse. The latest round of eclipses began on September 6 and will conclude on the 26th.

Now you know the reason for the blank frames – it’s a conspiracy by the Earth to block out the sun. The blackness is none other than the planet itself.

Normally the Earth is out of the way of the sun from SDO’s perspective but twice a year its orbit and Earth’s orientation to the sun cause Earth eclipses. Credit: NASA

Total eclipse happens every day between 1 and 2 a.m. local time (Mountain Daylight Time) when the Earth blocks the sun from SDO’s view. In similar fashion, we experience a solar eclipse on the ground when the moon covers up the sun. You can watch for pictures of the partial eclipse as Earth gets out of the way sometime next Tuesday the 25th by going to the SDO website. Follow these simple steps to find and view the images:

* Click on the Data tab and select AIA/HMI Browse Data
* Click on the Enter Start Date window, select a start date and click Done
* Click on Enter End Date and click Done
* Under Telescopes, pick the color (wavelength) sun you want
* Select Images in the display box
* Click Submit at the bottom and then browse the pictures

Not only does the Earth cross the sun from the observatory’s perspective, so does the moon (left) on occasion. The moon’s”bite” smaller and sharper. Earth’s atmosphere gives our planet a soft, diffuse edge compared to the airless moon’s. Photo at right was taken on September 6, 2012 at eclipse season start. Credit: NASA

While watching an eclipse of the sun by the Earth is one of the joys of living in the space age, there are other cool things to see from SDO’s perspective. Look at the drastic difference between the moon’s sharp outline and Earth’s fuzzy edge. Our planet “bites softly” into the sun because its substantial atmosphere grades from thick to thin, filtering the sunlight that passes through it. The moon’s a big baldy. With no air to grade and soften the light, the sun shines crisply right up to its edge.


Video of a partial eclipse of the sun by Earth. Refraction of light by Earth’s atmosphere causes the sun to bend at its edges. Credit: NASA SDO / Stanford University for HMI

We’ve seen how air can also bend or refract sunlight in strange ways, going so far as to “lift” the sun  into view when it’s still below the horizon.  You can see the same effect in a brand new way in this short video of an SDO partial eclipse. Watch the sun’s edge bend as the Earth rolls by. Compare it to a similar eclipse by the moon below.


Moon eclipsing sun via SDO 

SDO orbits about 22,000 miles above Earth, tracing out a figure-8 (called an analemma) above the Pacific and Mexico every 24 hours. Credit: NASA

SDO amazes with its spectacular pictures of the sun taken in 10 different wavelengths of light every 10 seconds; additional instruments study vibrations on the sun’s surface, magnetic fields and how much UV radiation the sun pours into space.

It’s the latest, greatest “Swiss Army knife” used by scientists to pry open the inner workings of the sun. The eclipses, while a gap in the data stream,  are a sweet bonus all their own.

My favorite Martian

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The first Martian (top) sighted on Mars smiles back from the rover’s calibration panel. The panel also features a 1909 Lincoln penny. Look closely at the penny and you’ll see a grain of Mars sand under Lincoln’s ear. It’s only 0.2 mm (.008 inches) across. Geologists classify sand grains this size as “fine sand”. Credit: NASA/JPL-Caltech/MSSS

Curiosity has traveled all of 466 feet along the dust, gravelly floor of Gale Crater since landing on August 6. It’s on its way to Glenelg to scoop up and analyze a soil sample. Earlier this week, mission controllers opened the recloseable dust cover on the Mars Hand Lens Imager (MAHLI) mounted on the rover’s robotic arm and snapped closeups of Curiosity’s underbelly, wheels and calibration target. The camera can focus on objects less than an inch away and acts as a magnifying glass similar to what a geologist would use in the field.

Wide view of Curiosity’s calibration target taken by the MAHLI imager. You can already see the orange coating of  Mars dust. Credit: NASA/JPL-Caltech/MSSS

My favorite photo of the bunch is the calibration target showing color reference swatches, a metric bar graphic, a penny and below it, a stair-step pattern for depth calibration. The 1909 VDB penny harks back to the geologists’ tradition of placing a coin,  rock pick or another object of known size in pictures of individual rocks or rock formations. It gives the viewer an idea of a feature’s size at a glance. Ken Edgett, MAHLI principal investigator, purchased the penny for the mission.

Moving in closer, we see there’s something else in the MAHLI image – a drawing of a Martian waving from a rock!

“Joe the Martian” is a character created by Edgett for the children’s science periodical “The Red Planet Connection” when Edgett directed the Mars outreach program at Arizona State University in the 1990s.

MAHLI photo of the underside of Curiosity with a view out to the horizon. Since the camera can focus anywhere from 0.8 inches all the way to infinity  it can capture both extreme closeups and landscapes. Credit: NASA/JPL-Caltech/MSSS

Joe goes back even further to when Edgett was 9 years old. He drew the character as part of a school project at the time of the 1975 Viking missions to Mars, the first to safely land probes on the planet. It was Viking that inspired him to become a Mars researcher. Joe’s appearance on Mars is most fitting.

Back in the 1960s I enjoyed watching episodes of My Favorite Martian, a TV sitcom about a Martian spaceship that crash lands near Los Angeles. Tim O’Hara, an LA Times reporter, discovers the wreck and the pilot, a Martian anthropologist dressed in a shiny aluminum jump suit. O’Hara nicknames him “Uncle Martin”. Antics ensue. Joe now joins Uncle Martin as my two favorite Martians.

12-mile-diameter Phobos nudges into the sun on September 13. Curiosity aimed its mastcam camera skyward and used a solar filter to take the photo. Credit: NASA

Digging through Curiosity’s stockpile of raw images today, I found this one taken by the mastcam of the moon Phobos partially eclipsing the sun on September 13. Nice bite!

Eclipse is slightly inaccurate. Because Phobos is so small, it’s technically called a transit. The little moon is only 3600 miles from Mars – much closer than the moon is from the Earth – so eclipses (transits) are fairly common.

According to Phil Plait of Bad Astronomy, Phobos crosses the sun about once a year from Curiosity’s site. Scientists  study transits of Phobos and Mars’ other moon Deimos to gauge the thickness of clouds and dust in the atmosphere. More images of the event should show up in the next few days. When they do, I’ll post a higher res version.


Transits of Phobos have been photographed before by the Mars Opportunity Rover. Click the video to see one recorded on November 9, 2010. 

Cool stuff to see during Tuesday’s transit of Venus

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A gorgeous image of this morning's partial lunar eclipse from southern Alberta photographed by author and astrophotographer Alan Dyer. This was the kind of eclipse chasing I like," said Dyer. "Just to the end of my driveway." Details: Canon 60Da and 18-200mm Sigma lens at 115mm and at f/5.6 for 0.4 sec at ISO 160. Copyright: Alan Dyer

Soon the trifecta will be complete. Originally a horse racing term, but now often used to refer to three important things coming together at the same time, tomorrow’s transit of Venus will be the third in a series of celestial alignments that included the May 20 annular eclipse of the sun and this morning’s partial lunar eclipse.

Although I got up at 4:45 a.m. with hopes of seeing the moon touched by Earth’s shadow, clouds eclipsed the entire sky. I hope some of you were more fortunate. The weather looks good in my neighborhood for tomorrow’s (June 5) Venus transit, which across North America begins within a couple minutes of 22:05 Universal time or 6:05 Eastern Daylight, 5:05 p.m. Central, 4:05 p.m. Mountain and 3:05 Pacific time.

In Duluth, Minn. we should see the first sign of Venus’ silhouetted self touch the northeastern limb of the sun at 5:04 p.m. This moment is called first contact. 18 minutes later the opposite side of the planet will touch the inner limb of the sun at second contact. A little more than 6 hours later Venus will again touch the inner limb on the western side of the sun during third contact before slowly exiting the sun’s disk (fourth contact).  While you may applaud at transit end, don’t expect an encore until the year 2117.

Black polymer eclipse glasses are great for observing the transit. Venus will be visible as a very small black dot without optical aid. Photo: Bob King

By now, you’ve probably planned out how you’re going to view the event. Methods include special mylar or glass filters coated to reduce the sun’s light UV and infrared light to a safe level. You can also use a #14 welders glass, pinhole projection using a cardboard box or project the sun’s image onto white poster board with binoculars. If you plan on projecting the sun’s image and still need help on how, click HERE for an excellent guide.

It’s important to set up at least a half hour before the transit begins, so you don’t miss the first 20 minutes and /or the last 20 minutes, arguably the most exciting times for viewing. Here are things to watch for:

Venus' atmosphere shows as a bright rim just beyond the sun in the picture taken by the Transition Region and Coronal Explorer (TRACE) spacecraft during the 2004 transit. Credit: NASA

* Aureole of Venus’ atmosphere – This is a faint, extremely narrow annulus or ring of light visible around the planet at first contact through a telescope. Use as high a magnification as possible without blurring the image.  As Venus moves farther into the sun, the ring will shrink to a arc and then disappear.

What you’re seeing is Venus’ thick atmosphere backlit by the brilliant sun. The air on Venus is mostly carbon dioxide and about 100 times as dense as Earth’s. Lower down, clouds of sulfuric acid sprinkle the red-hot, 800-degree surface with a particularly nasty version of acid rain. The sequence of events are reversed during third and fourth contacts.

Venus’ ring is very similar to the ring of light around the Earth that an astronaut on the moon would see when we on Earth experience a total lunar eclipse. Picture the astronaut watching the big silhouetted Earth cover the sun, its circumference aglow with the oranges and reds of low-angled sunlight. That very same light, bent by the atmosphere into Earth’s shadow, colors the moon during eclipse.

You can create a similar black drop effect with your fingers. Photo: Bob King

* Black drop effect — I described this in an earlier blog, but let’s have one more go at it. As the last bit of Venus moves into the sun’s disk at second contact, you might see the planet momentarily shaped like a teardrop. The side of Venus’ disk closest to the sun’s inner limb will appear to stretch toward it momentarily as a black ligament before “snapping” free.

You can see a similar effect by holding out a hand against a smooth, light backdrop and barely touching thumb and index finger. It’s caused by a combination of blurring from turbulence in Earth’s atmosphere and the natural darkening along the sun’s inner edge.

* Blackness of planet vs. sunspots — Venus will easily win out for being blacker than the darkest sunspots. As of this morning there are seven sunspot groups out, so it’ll be easy to compare.

* Happy alignment — Expand your mind and picture the whole scene as you’d see it far above the Earth in outer space with the sun, Venus and Earth, Venus all sitting pretty in a row.

If it’s cloudy at your place tomorrow,  you can always watch the live NASA webcast. Locally here in Duluth, the Marshall W. Alworth Planetarium on the UMD campus will have people and telescopes on hand for anyone wanting to come by for a look starting at 5 p.m.

Tomorrow we’ll look at what scientists hope to learn from the transit.

Lunar eclipse only hours away

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The full moon rises atop Earth's rising shadow in early spring 2010. The full moon tomorrow morning June 4 will undergo a partial eclipse. Photo: Bob King

All ready for tomorrow morning’s partial lunar eclipse? Earth’s shadow will cover a maximum of 37% of the moon shortly before and after sunrise for the Midwest, South and and Western U.S. You might be scratching your head wondering if it’s worth getting up at 4  or 5 a.m. to see such a wimpy eclipse. I understand your reluctance. We all have our thresholds.

While I might drive a couple hundred miles for a total lunar eclipse, I wouldn’t for a minor partial. Here in Duluth, Minn. only a few percent of the moon will be covered before it sets shortly after sunrise. If skies are clear, I’ll still be out there. Just about any eclipse is rare enough to expend some effort. After all, the next one – a total – won’t happen until April 2014. And honestly, I like the picture in my head of sun, Earth, moon and me all lined up.

The shadow of the planet rises into the sky for an observer facing east as the sun sets in the west. The situation's reversed for the rising sun, with the shadow in the west as the sun rises in the east. Illustration: Bob King

Eclipses are about shadows. We can see the cause of this eclipse anytime it’s clear around sunset. Face opposite the setting sun and you’ll see a long, purple-gray band rising in the eastern sky. That’s the Earth’s shadow. Standing here on the planet, the shadow rises and eventually fills most of the sky by local midnight. We don’t see it at night of course because it’s dark out and the shadow blends into the sky.

The Earth's shadow has two parts, the dark inner umbra and the outer penumbra.The penumbra is not fully dark because a portion of the sun shines into it. Credit: image courtesy of Courtney Seligman

We can see the space station and other satellites disappear into or re-appear out of the shadow on many nights depending on the satellite’s altitude and season of the year.

If we could see the Earth's shadow at the moon's distance it would look like this - a double bullseye covering a surprisingly small patch of sky. Shadow size is approximate. Created with Stellarium

Earth’s shadow stretches out behind the planet to the moon and beyond. At the moon’s average distance of 239,000 miles, Earth’s two-part shadow, consisting of the dark umbra and sun-touched penumbra, covers only about 2.3 degrees of sky or a bit less than five full moons lined up side by side.  The distance between the two stars at the end of the bowl of the Big Dipper is twice as wide. That’s a small target.

Times and the moon's path through the outer part of Earth's umbra are shown for tomorrow morning. Add an hour for Eastern time, subtract an hour for Mountain and two hours for Pacific. Credit: Tom Ruen with my own additions

Since the moon’s orbit is inclined to the Earth’s, it easily misses the shadow most full moons. Only occasionally does it hit the mark.

If you’ve been following the transit of Venus updates, you’ll recall that Venus’ inclined orbit is the reason transits are so rare. The same is true with the moon.

I hope you do take a look at tomorrow’s  eclipse. Don’t let the routine early risers have all the fun. For more details on the event, check out my earlier blog and this NASA pdf file.

Tycho (button-like crater below and left of center) and its rays dipped in the colors of another partial eclipse on August 16, 2008. Click photo to see more eclipse photos. Thanks and credit to: Pedro Ré

During the eclipse, you’ll see the shadow cover the bottom or southern half of the moon. This is Tycho territory. Tycho, a 53-mile- diameter crater, is crowned with the most spectacular and largest halo of “rays” of any lunar crater. The rays formed when material from the impact that created Tycho rained back down onto the moon’s surface to excavate strand upon strand of fresh secondary craters. Tycho and its rays, normally a blaze of white streaks centered on the brilliant crater at full moon, will be tempered a mellow yellow and orange during eclipse.

SpaceX launch aborted plus solar eclipses for your bucket list

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The SpaceX Falcon 9 rocket ignites its nine engines for a few seconds before shutting them down this morning. Credit: NASA TV

It huffed and it puffed but never took to the sky. Today was to be the historic launch of the Falcon 9 rocket and Dragon capsule to the International Space Station (ISS), but a mere half-second before liftoff, on-board computers shut it down. Launch aborted. A high pressure reading in the combustion chamber in engine #5 was to blame.

Tuesday May 22 at 2:44 a.m. Central time is the next earliest launch opportunity. Fortunately a spare engine – Falcon runs with a total of nine – is available as a replacement if needed. Falcon is the first attempt by the private American company SpaceX to get into the ISS cargo-delivery business, a task that to date has been handled by government-run space programs in Russia, Japan, Europe and the U.S.

Artist rendering of SpaceX Dragon spacecraft being berthed on the Harmony module of the space station. Credit: NASA

The company was founded by billionaire Elon Musk, the fellow who helped start Paypal. Once launched successfully, Falcon will send the Dragon capsule into orbit near the space station, where it will perform check-out procedures before attempting a rendezvous. SpaceX’s longer term goal is to develop a ship to ferry astronauts to and from the ISS, a task handled by the Russians for the time being.

According to NASA, the primary objectives for the Falcon mission include a flyby of the space station at a distance of approximately 1.5 miles to validate the operation of sensors and flight systems necessary for a safe rendezvous and approach, including abort procedures. If it passes those tests, mission control will clear it for berthing with the station.

Dragon will later return to Earth, splashing down in the Pacific Ocean with space station equipment and experiments. Let’s hope launch is a go next Tuesday. Because of the delay, there’s a chance of seeing Dragon chase the ISS across the sky for U.S. observers. The space station returns to the dawn sky beginning Tuesday (maybe a little earlier or later depending on your location). I’ll have details on how to watch for it soon.

Tomorrow’s annular eclipse is oh-so-close. I hope you’re well-prepared for what will be the last solar eclipse visible from the U.S. until October 23, 2014. That will only be partial at best with a maximum of 81% of the sun covered. Interestingly, it will also occur around sunset as seen from the Midwest and central Canada.

Path of the total eclipse on August 21, 2017. GE is short for Greatest Eclipse, the location where totality lasts longest. Credit: NASA

The eclipse following that one is the BIGGIE – a total eclipse on August 21, 2017. The path of totality begins in northern Oregon and continues through Idaho, Wyoming, Nebraska, Missouri, southern Illinois, Tennessee and South Carolina. Lots of great opportunities and places to see that one!

And if you can hang in there long enough, another total eclipse will grace the western U.S. only six years later on October 14, 2023.

Live in the Midwest? Enjoy a rare sunset solar eclipse

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If you live in the gray band or are planning a trip there, you'll see the full annular eclipse. The red line shows where the moon will pass squarely over the sun's face. Click map to see an interactive version where you can click on your city to get local times and coverage for the eclipse. See below for more local times. Credit: NASA

Most of us won’t be in the path of the annular eclipse that cuts across the western U.S. this Sunday afternoon. That means we’ll see varying degrees of a partial eclipse. The farther west and south you are, the more of the sun will go missing. Across the Midwest, about 2/3 of the sun will be covered at maximum eclipse.  Viewed through a safe solar filter or indirectly, by projecting the sun’s image onto a sheet of white paper with binoculars, the eclipsed sun will be a lovely sight.

If you still would like to observe the sun directly but can’t find a mail-order solar filter, contact your local welding supply store and purchase a #14 welder’s glass.

Much of the U.S and Canada, will see a rare partial eclipse at sunset Sunday. This photo is from the June 10, 2002 eclipse. Credit: Christopher Go

For a wide swath of the central U.S. and Canada, the sun sets while still in eclipse, giving us a rare and scenic opportunity to observe a most unique sunset. I may be stuck in Duluth, but you better believe I’ll be somewhere where I can see right down to the northwestern horizon Sunday night.

Consider hunting up a similar spot where you live. Take the family and friends and arrive a little before eclipse start. My guess is that you’ve photographed sunsets before; this time your sun will take on a whole new appearance. If you stick around into twilight, you’ll even be able to see Venus a little more than “two fists” above and left of the sunset point. Binoculars will show it as a tiny crescent moon.

View of Sunday's partial solar eclipse from Duluth, Minn. At maximum eclipse at 8:17 p.m., the sun will be only 3 degrees or "two fingers" above the horizon. The sun sets while still in eclipse. Created with Chris Marriott's SkyMap

The whole event happens in the early evening with the sun low in the western sky.  For Duluth, Minn. the moon takes it first nibble of the solar cookie at 7:17 p.m. when the sun is only 12 degrees high or about a balled fist held at arm’s length against the sky. Maximum eclipse – when the most sun is covered – occurs an hour later at 8:17 p.m., when 66% of the sun’s disk is blocked.

Even though our weather forecast is grim, Sunday night is expected to clear out. Because clear skies often start in the west and move east, the sun sometimes pops out at sunset from beneath the blanket of clouds. Don’t miss it.

Here’s a sampling of eclipse times for major cities not in the annular path but that will still experience a nice partial eclipse. The listed times are local, meaning the time you see on your watch or cellphone if you live there.  Eclipse start and maximum coverage times are shown:

* Minneapolis, Minn. — 7:19 p.m. start / 8:19 p.m.  max / 67% covered / Sun sets in eclipse
* Fargo, ND — 7:16 p.m. / 8:18 p.m. / 66% / Sun sets in eclipse
* Winnipeg, Manitoba — 7:13 p.m. / 8:14 / 61% / ”     ”
* Madison, Wis. —  7:21 p.m. / 8:20 p.m. /  68% / ”     ”
* Chicago, Ill. — 7:22 p.m. / 8:21 p.m. / 69% / ”     ”
* Detroit, Mich. — 8:21 p.m. Sun only 4 degrees high at start and sets before maximum
* Indianapolis, Ind. — 8:24 p.m. with sun 5 degrees high. Sets before max.
* Memphis, Tenn. — 7:29 p.m. with sun 5 degrees high. ”     ”
* Montgomery, Ala. — 8:30 p.m. with sun only 1 degree high. ”     ”
* Omaha, Neb. — 7:23 p.m / 8:25 / 76%
* Kansas City, Kan. — 7:25 p.m. / 8:27 p.m. /  79% Max. eclipse happens at sunset
* Denver, Colo. — 6:23 p.m. / 7:30 p.m. / 86%
* Dallas, Tex. – 7:32 p.m. / max eclipse of 94% occurs ~12 mins. after sunset
* Salt Lake City, Utah — 6:19 p.m. / 7:30 / 89% / Eclipse ends just before sunset
* Las Vegas, Nev. — 5:24 p.m. / 6:36 p.m. / 92% / Eclipse ends at sunset
* Billings, Mont. — 6:14 p.m. / 7:22 p.m. / 77% Eclipse ends before sunset
* Seattle, Wash. — 5:02 p.m. / 6:18 p.m. / 83% Eclipse ends before sunset
* Portland, Ore. — 5:04 p.m. / 6:21 p.m. / 88% ”      ”

Morning crescent moon anticipates weekend solar eclipse

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The sky facing east tomorrow morning about an hour before sunrise. The moon will appear as a beautiful crescent. Created with Stellarium

As the solar eclipse approaches, we watch with anticipation as the moon slims to a thin crescent in the morning sky. Each day it slips a fist eastward toward the sun as if drawn by a tractor beam toward Sunday evening’s eclipse.

Tomorrow the moon will be appear in the rosy glow of dawn in the east below the familiar Great Square of Pegasus, a baseball-diamond shaped constellation prominent during fall evenings.  Watch for it if you’re up with the birds.

The May 5 full moon occurred when the moon was closest to the Earth or perigee; new moon happens 2 weeks later at apogee, when the moon is farthest away. Illustration: Bob King

A reader asked about why the moon is now so far from Earth (at apogee) when we just had a perigee or unusually close full moon.

If you recall that the moon’s orbit is an ellipse with Earth a little off to one side of center, perigee and apogee are directly opposite one another.  Since the moon orbits the planet in about four weeks, when perigee (closest approach) occurs at full moon, it’s a given that apogee will be half an orbit or about two weeks later.

Total solar eclipse August 11, 1999 occurred when the moon was near perigee. Credit: Luc Viatour

Guess what phase the moon’s in two weeks after full? New moon! And it’s only at new moon, when the moon slides between the Earth and the sun, that a solar eclipse is possible. This month’s new moon happens when it’s most distant from Earth. Its smaller apparent diameter can’t fully hide the sun, giving us an annular eclipse.

When a new moon happens around perigee, it’s more than big enough to cover the sun. That’s why the November 13 eclipse over northern Australia will be a total one. New moon occurs just a day before perigee.

How to safely view the upcoming solar eclipse and transit of Venus

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Safe solar filters for looking at the sun come in several different varieties. Read down to learn more about each kind. Photo: Bob King

We have two wonderful events involving the sun in the next few weeks – a solar eclipse on May 20 and the passage of Venus directly across the sun’s face on June 5. You’ll want to get ready for both by purchasing a simple, safe solar filter.

Observers inside the band bounded by the blue lines will see the May 20 annular solar eclipse. The red line shows the even narrower strip where the moon will be perfectly centered on the sun. Click map to go to the interactive version. Credit: Fred Espenek / NASA

On Sunday afternoon and evening May 20,  sky watchers living in a noodle-like strip from southern Oregon through western Texas will witness an annular (ring) eclipse of the sun. Because the moon will be just one day past apogee or farthest from Earth, it’s too small to completely cover the sun. Like a lid too small to cover the pot, a ring of sunlight remains around the silhouette of the new moon. Unlike a total solar eclipse, when you can safely view the sun without a filter for a few minutes during totality, you’ll need to protect your eyes throughout this eclipse.

Annular eclipse of Oct. 3, 2005. Credit: Sancho_Panza

If you live outside the approximately 150-mile wide noodle, don’t worry. Most of the U.S. and Canada will experience a partial eclipse except for the East Coast, where the sun will have already set. The sun will be 63% covered in my town of Duluth, Minn. and set while still in eclipse.

The second event is the transit or passage of Venus across the face of the sun happening during afternoon and evening hours on June 5 for the U.S. and Canada. Venus transits come in pairs – the last pair was in December 1874 and December 1882. The first of the current set began with a transit on June 8, 2004. If you miss the June 2012 event, you’re almost certain to be in your grave for the next transit in December 2117.

Transit of Venus on June 8, 2004 photographed through a small telescope. Venus will also be visible in binoculars and with the naked eye with a suitable solar filter. Click photo to go to my blog devoted to the Venus transit. Photo: Bob King

I’ll have much more information on each event in the coming days, but for now it’s important to prepare.  Since both involve looking at the sun, you’ll need eye protection in the form of a SAFE solar filter. The sun emits dangerous infrared (heat) and UV radiation. While our skin can handle the effects outside of the occasional sunburn, our eyes cannot. If you still directly at the sun, you’ll fry your retinas and not even know it, since they lack pain receptors.

Special “eclipse glasses” or a #14 welder’s provide a safe and convenient way to view the sun. Both block 99.99% of the sun’s light and cost only a few dollars. My personal favorite are the eclipse glasses made with an optical-quality plastic called black polymer. They provide a sharp, pleasing image of the sun.  Aluminized plastic filters made of  mylar also work well. Welder’s glass gives a green solar image, mylar a blue one and black polymer a light orange.

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. Photo: Bob King

Safe, screw-on solar filters are available for camera lenses if you’re thinking about taking pictures of the events.  Or you can buy individual sheets of polymer or mylar and rubber-band them around your lens.

Telescope users can choose from a wide variety of mylar or glass filters mounted in caps that fit snugly over the objective lens.

Here are basic DOs and DON’Ts when it comes to safely observing the sun:

DO NOT use smoked glass, old photographic negatives, sunglasses or shiny mylar helium balloons to view the sun. They allow dangerous radiation to pass through to your eyes.

DO NOT stack lower numbered welder’s glasses to “create” a #14.  Use #14 ONLY.

DO NOT put on eclipse glasses and look through an unfiltered telescope. They’ll melt and expose your eyes to concentrated sunlight in seconds!

DO NOT place solar filters over the eyepiece of a telescope. They’ll melt or crack in the concentrated sunlight. Place filters ONLY over the objective end of the scope.

And now for a few DOs:

DO observe the sun as long as you like through a safe filter.

DO wrap and secure a safe solar filter around each objective lens on the FRONT end of your binoculars for a crisp, magnified view of the sun.

DO build a simple pinhole projector to view the sun safely without a filter. Instructions HERE.

DO use optical projection to project a big, bright image of the sun from binoculars or telescope onto a sheet of white cardboard. Instructions HERE.

And now you need a SAFE solar filter. Below I’ve listed several websites where you can purchase one. You can also check online and in the yellow pages of the phone book for a local welding supply store and request a #14 welder’s glass.

* Thousand Oaks Optical — A large variety of solar filters for telescopes and cameras. Sheets of black polymer and other materials are available in several different sizes if you want to make your own.
* Rainbow Symphony — Eclipse glasses and solar viewers as well as filters for binoculars and telescopes. The most basic glasses are cheap  at just 85 cents apiece, but you’ll need to purchase a minimum of 25 pairs. A mounted piece of #14 welder’s glass or coated optical glass costs $20.
* Opt Corp — Offers high-quality Baader mylar optical filter material. Cost: $35 for a 10-inch by 10-inch sheet.
* Orion Telescopes — Glass solar filters for telescopes and binoculars. Baader filter material available for 4.5″ telescopes.

* Amazon.com – Safe solar eclipse viewers for naked eye use

Tiny gaps along the length of this palm frond created a series of solar crescents during the July 1991 eclipse. Photo: Bob King

If for some reason you aren’t able to get a solar filter, all is not lost. The tiny spaces between leaves on a tree act like pinhole projectors and will cast hundreds of images of the sun on the ground below during the eclipse. To see the effect even better, bring along a white sheet or blanket and spread it out beneath the tree. You can even cross your hands over one another at right angle to create a pattern of small “holes” that will reveal the changing shape of the sun as the eclipse proceeds.