Observing Archives

October 23, 2015December 23, 2015 by David Dickinson

Seeing Starspots: The Curious Case of XX Trianguli

Ever wonder what happens on the surface of other stars?

An amazing animation was released this week by astronomers at the Leibniz Institute for Astrophysics (AIP) in Potsam Germany, showing massive sunspot activity on the variable star XX Trianguli (HD 12545). And while ‘starspot’ activity has been seen on this and other stars before, this represents the first movie depicting the evolution of stellar surface activity beyond our solar system.

“We can see our first application as a prototype for upcoming stellar cycle studies, as it enables the prediction of a magnetic-activity cycle on a dramatically shorter timescale than usual,” says Leibniz Institute for Astrophysics Potsdam astronomer Andreas Kunstler in a recent press release.

The images were the result of a long term analysis of the star carried out using the twin STELLA (STELLar Activity) robotic telescopes based on Tenerife in the Canary Islands. The spectroscopic data was gathered over a period of six years, and this video demonstrates that, while other stars do indeed have sunspot cycles similar to our Sun, those of massive stars such as XX Tri are much more intense than any we could imagine here in our own solar system.

Image credit: Leibniz Institute for Astrophysics Potsdam (AIP) — STELLA on the hunt. Image credit:

Even the largest and closest of stars have a minuscule angular diameter –measured in milliarcseconds (mas, our 1/1,000ths of an arc second)—in size. For example, we know from lunar occultation timing experiments that the bright star Antares at 550 light years distant and 5 times the radius of our Sun is about 41 mas in size. At an estimated 910 to 1,500 light years distant and 10 times the radius of our Sun, XX Tri is probably comparable, at about 20 mas in size.

That’s tiny from our perspective, though the massive starspot depicted must be truly gigantic to see up close.

To image something on that scale, astronomers use a technique known as Doppler tomography gathered from high-resolution spectra. Over said six year span covering a period from July 2006 to April 2012, 667 viable spectra were gathered, covering 86 total rotational periods for the star. Incidentally, that’s not much longer than the average equatorial rotational period of our Sun—remember, as a ball of gas, the rotational period of our Sun varies with solar latitude—at about 22 days.

Our relatively sedate host star. image credit: Dave Dickinson — Our relatively sedate host star. Image credit: Dave Dickinson

The views compiled by the team show a pole facing, Mercator projection, and a spherical ‘real view’ of the star. Of course, to see XX Tri up close would be amazing, if a not a little intimidating with those massive, angry spots dappling its surface.

Watch the animation, and you can see the changing morphology of the spots, as they decay, merge and defuse again. Just how permanent is that massive pole spot? Why are we seeing spots across the pole of a star like XX Tri at all, something we never see on the Sun? Do other stars follow something analogous to Spörer’s Law and their own version of the 11-year sunspot cycle that we see on Sol?

Capabilities such as those demonstrated by STELLA may soon crack these questions wide open. Composed of two 1.2 meter robotic telescopes jointly operated by the Institute for Astrophysics at Potsdam and the Instituto de Astrofísica de Canarias (IAC), STELLA combines the capability of a wide-field photometric imager with that of a high-resolution spectrograph, ideal for this sort of analysis of remote stellar surfaces.

A diagram featuring the twin STELLA instruments. Image credit: Leibniz Institute for Astrophysics Potsdam (AIP)

Hey, here’s a crazy idea: turn STELLA loose on KIC 8462852 and see if the hypothesized ‘exo-comets’ or ‘alien mega-structures’ turn up… though it weighs in much smaller than XX Tri at 1.4x solar masses, KIC 8462852 is also about 1,400 light years distant, perhaps just doable using high resolution spectroscopy…

Want to see XX Tri for yourself? An RS Canum Venaticorum variable orange giant star (spectral type K0 III) located in the constellation of Triangulum the Triangle, XX Tri shines at magnitude +8.5 and varies over about half a magnitude in brightness. Its coordinates are:

Right Ascension: 2 hours 3 minutes 47 seconds

Declination: 35 North 35 minutes 29 seconds

The more we learn about other stars, the more we understand about how to live with our very own sometimes placid, sometimes tempestuous host star.

Read more about the curious case of XX Trianguli:

–On the Starspot Temperature of HD 12545

–HD 124545: A Study in Spottedness

–Spot evolution on the Star XX Triangulum (sic)

Does XX Trianguli look familiar? That might be because it was featured as the Astronomy Picture of the Day as ‘imaged’ by the Coude Feed Telescope on Kitt Peak way back when on November 2nd, 2003.

October 22, 2015December 23, 2015 by David Dickinson

Can Lunar Earthshine Reveal Ashen Light on Venus?

A recent celestial event provided a fascinating look at a long-standing astronomical mystery.

Is the ‘ashen light of Venus’ a real phenomena or an illusion?

On October 8^th, the waning crescent Moon occulted (passed in front of) the bright planet Venus for observers in the southern hemisphere. And while such occurrences aren’t at all rare—the Moon occults Venus 3 times in 2015, and 25 times in this decade alone worldwide—the particulars were exceptional for observers in Australia, with a -4.5 magnitude, 40% illuminated Venus 30” in size emerging under dark skies 45 degrees west of the Sun from behind the dark limb of the Moon.

David and Joan Dunham rose to the challenge, and caught an amazing sequence featuring a brilliant Venus reappearing from behind the Moon as seen from the Australian Outback. When I first watched the video posted on You Tube by International Occultation Timing Association (IOTA) North American coordinator Brad Timerson, I was a bit perplexed, until I realized we were actually seeing the dark nighttime side of a waning Moon, with the bright crescent just out of view. Venus fully emerges in just under a minute after first appearing, and its -4^th magnitude visage shines like a spotlight when revealed in its full glory.

“Joan and I observed the reappearance of Venus from behind the dark side of the 15% sunlit waning crescent Moon, from a dark and wide parking area on the east side of the Stuart Highway that afforded a low (1-2 degree) horizon to the east,” Dunham said. “Since the past observations of ashen light were visual, I decided that it would be best to use the 25mm eyepiece with the 8-inch visually rather than just make a redundant video. Neither the real-time visual observation, nor close visual inspection of the video recording, showed any sign of the dark side of Venus.”

We’ve written about the strange puzzle of ashen light on the nighttime side of Venus previously.

Reports by visual observers of ashen light on the dark limb of Venus over the centuries remain a mystery. On the crescent Moon, it’s easy to explain, as the Earth illuminates the nighttime side of our natural satellite; no such nearby illumination source exists in the case of Venus. Ashen light on Venus is either an illusion—a trick of the dazzling brilliance of a crescent Venus fooling the eye of the observer—or a real, and not as yet fully described phenomenon. Over the years, suggestions have included: lightning, airglow, volcanism, and aurora. A good prime candidate in the form of an ‘auroral nightglow” was proposed by New Mexico State University researchers in 2014. 19^th century astronomers even proposed we might be seeing the lights of Venusian cities, or perhaps forest fires!

Could we ever separate the bright crescent of Venus from its nighttime side? A lunar occultation, such as the October 8^th event provides just such a fleeting opportunity. Though it’s hard to discern in the video, Dunham also watched the event visually through the telescope, and noted that, in his words, “the dark side of Venus remains dark,” with no brief appearance prior to sighting the crescent shining through the lunar valleys.

A tentative light curve made by Mr. Timerson seems to support this assertion, as the appearance of Venus quickly over-saturates the view:

Of course, this is far from conclusive, but seems to support the idea that the ashen light of Venus noted by ground observers is largely an optical illusion. Not all occultations of Venus by the Moon are created equal, and the best ones to test this method occur when Venus is less than half illuminated and greater than 40 degrees from the Sun against a relatively dark sky. Compounding problems, the ‘dark’ limb of the Moon has a brightness of its own, thanks to Earthshine. Dunham notes that observers in southern Alaska may have another shot at seeing this same phenomenon on December 7^th, when the 13% illuminated crescent Moon occults a -4.2 magnitude 69% illuminated Venus, 42 degrees west of the Sun… the rest of North and South America will see this occultation in the daytime, still an interesting catch.

Looking at future occultations, there’s an intriguing possibility to hunt for the ashen light on the evening of October 10^th, 2029, when then Moon occults a 57% illuminated Venus against dark skies for observers along the U.S. West Coast. Incidentally, a dawn occultation provides a better circumstance than a dusk one, as Venus always reemerges from the Moon’s dark limb when it’s waning. It enters the same when waxing, perhaps allowing for observer bias.

Can’t wait for December? The Moon also occults the bright star Aldebaran on October 29^th for Europe and North America on November 26^th near Full phase… the good folks at the Virtual Telescope will carry the October event live.

For now, the ashen light of Venus remains an intriguing mystery. Perhaps, an airborne observation could extend the appearance of Venus during an occultation, or maybe the recently announced Discovery-class mission to Venus could observe the night side of the planet for an Earthly glow… if nothing else, it’s simply amazing to watch the two brightest objects in the nighttime sky come together.

October 14, 2015December 23, 2015 by David Dickinson

Is This Month’s Jupiter-Venus Pair Really a Star of Bethlehem Stand In?

Image credit and copyright: Clapiotte Astro

Eclipse tetrads of doom. Mars, now bigger than the Full Moon each August. The killer asteroid of the month that isn’t. Amazing Moons of all stripes, Super, Blood, Black and Blue…

Image credit and copyright: @TaviGrainer(ck) — Venus, Mars, Jupiter and the Moon from October 9th. Image credit and copyright: @TaviGreiner

The internet never lets reality get in the way of a good meme, that’s for sure. Here’s another one we’ve caught in the wild this past summer, one that now appears to be looking for a tenuous referent to grab onto again next week.

You can’t miss Jupiter homing in on Venus this month, for a close 61.5’ pass on the morning on Oct 25^th. -1.4 magnitude Jupiter shows a 33” disk on Sunday’s pass, versus -4 magnitude Venus’ 24” disk.

Oct 26 Stellarium — Looking east on the morning of October 26th. Credit: Stellarium

We also had a close pass on July 1^st, which prompted calls of ‘the closest passage of Venus and Jupiter for the century/millennia/ever!’ (spoiler alert: it wasn’t) Many also extended this to ‘A Star of Bethlehem convergence’ which, again, set the web a-twittering.

Will the two brightest planets in the sky soon converge every October, in the minds of Internet hopefuls?

This idea seems to come around every close pass of Jupiter and Venus as of late, and may culminate next year, when an extra close 4’ pass occurs on August 27^th, 2016. But the truth is, close passes of Venus and Jupiter are fairly common, occurring 1-2 times a year. Venus never strays more than 47 degrees from the Sun, and Jupiter moves roughly one astronomical constellation eastward every Earth year.

Much of the discussion in astrological circles stems from the grouping of Jupiter, Venus and the bright star Regulus this month. Yes, this bears a resemblance to a grouping of the same seen in dawn skies on August 12^th, 2 BCE. This was part of a series of Jupiter-Venus conjunctions that also occurred on May 24^th, 3 BCE and June 17^th, 1 BCE. The 2 BCE event was located in the constellation Leo the Lion, and Regulus rules the sign of kings in the minds of many…

Stall — Looking eastward on the morning of August 12th, 2 BCE. Credit: Stellarium

But even triple groupings are far from uncommon over long time scales. Pairings of Jupiter, Venus in any given zodiac constellation come back around every 11-12 years. Many great astronomical minds over the centuries have gone broke trying to link ‘The Star’ seen by the Magi to the latest astronomical object in vogue, from conjunctions, to comets, to supernovae and more. If there’s any astronomical basis to the allegorical tale, we’ll probably never truly know.

The October 25th pass of Venus vs Jupiter. Created using Starry Night Education software.

Aaron Adair, the author of The Star of Bethlehem: A Skeptical View has this to say to Universe Today:

“The 3/2 BCE conjunctions don’t fit the time of Jesus’ birth. There is also no evidence that these sorts of conjunctions were considered all that good; I even found evidence that they were bad news for a king, especially if Jupiter was circling around Regulus. And of course, none of this even comes close to doing the things the Star of Bethlehem was claimed to have done.

So, we have a not terribly rare situation in the sky that conforms to something that doesn’t really fit the Gospel story in a time frame that doesn’t fit the Jesus chronology which doesn’t really have anything all that auspicious about that to ancient observers.”

The dance of the planets also gives us a brief opening teaser on Saturday morning, as Mars passes just 0.38 degrees NNE of Jupiter on Oct 17^thlooking like a fifth pseudo-moon.

Finally, the crescent Moon joins the scene once again on November 7^th, passing 1.9 degrees SSW of Jupiter and 1.2 SSW of Venus, a great time to attempt to spy both in the daytime using the crescent Moon as a guide. And keep an eye on Venus, as the next passage of the crescent Moon on December 7^th features a close grouping with binocular Comet C/2013 US10 Catalina as well.

How close can the two planets get?

Stick around ‘til November 22^nd 2065, and you can watch Venus actually transit the face of Jupiter:

Though rare, such an occlusion involving the two brightest planets happens every other century or so… we ran a brief simulation, and uncovered 11 such events over the next three millennia:

Bruce McCurdy of the Royal Canadian Astronomical Society posed a further challenge: how often does Venus fully occult Jupiter? We ran a simulation covering 9000 BC to 9000 AD, and found no such occurrence, though the July 14^th, 4517 AD meeting of Jupiter and Venus is close.

Let’s see, I’ll be on my 3^rd cyborg body, in the post- Robot Apocalypse by then…

This sort of total occlusion of Jupiter by Venus turns out to be rarer than any biblical conjunction. Why?

Well, for one thing, Venus is generally smaller in apparent size than Jupiter. When Jupiter is near Venus, it’s also near the Sun and in the 30-35” size range. Venus only breaks 30” in size for about 20% of its 584 synodic period. But we suspect a larger cycle may be in play, keeping the occurrence of a large Venus meeting and covering a shrunken Jove in our current epoch.

A Moon, a star, three planets and... a space station? A close pass of Tiangong-1 (arrowed) near this month's grouping. Image credit: Dave Dickinson — A Moon, a star, three planets and… a space station? A close pass of Tiangong-1 (arrowed) near this month’s grouping. Image credit: Dave Dickinson

Astronomy makes us ponder the weirdness of our skies gracing our backyard over stupendously long time scales. Whatever your take on the tale and the modern hype, be sure to get out and enjoy the real show on Sunday morning October 25th, as the brightest of planets make for a brilliant pairing.

October 7, 2015December 23, 2015 by Bob King

Guide to October’s Conjunction Mania, See Venus in Daylight

The sky sparkles with the Moon (top, overexposed), Regulus, Venus, Mars, and Jupiter at dawn this morning October 7, 2015.

Tomorrow morning might be a good time to call for extra celestial traffic control. A slip of a crescent Moon will join a passel of planets in the dawn sky for the first of several exciting conjunctions over the next few days.

Facing east about 1 1/2 hours before sunrise Thursday morning Oct. 8. Let your eyes delight in the river of Moon and planets. Source: Stellarium — The scene facing east about 1 1/2 hours before sunrise Thursday morning Oct. 8. Let your eyes delight in the tumble of Moon and planets. Source: Stellarium

In the space of three mornings beginning tomorrow, four planets, the Moon and the star Regulus will participate in six separate conjunctions. Here’s how it’ll play out. Time are shown in UT / Greenwich Mean Time and Central Daylight and 1° equals two full moon diameters:

October 8: Venus 2.5° south of Regulus at 18 UT (1 p.m. CDT)
October 8: Regulus 3.1° north of the moon at 19 UT (2 p.m. CDT)
October 8: Venus 0.6° north of the moon at 20 UT (3 p.m. CDT)
October 9: Mars 3.2° north of the moon at 14 UT (9 a.m. CDT)
October 9: Jupiter 2.5° north of the moon at 21 UT (4 p.m.)
October 11: Mercury 0.8° north of the moon 11 UT (6 a.m. CDT)

The crescent Moon will be near Venus all day Thursday for the Americas until it sets in late afternoon, making for a great opportunity to catch sight of the planet in the middle of the day. This binocular view is for noon CDT Oct. 8 when the planet lies just shy of 2 from the Moon. Source:: Stellarium — The crescent Moon will be near Venus all day Thursday for the Americas until it sets in late afternoon. What a great opportunity to catch sight of the planet in the middle of the day. This binocular view depicts their arrangement around noon CDT Oct. 8, when the planet lies less than 2° from the Moon. Source:: Stellarium

Since several of the events occur in the middle of the afternoon for skywatchers in the Americas, here’s an expanded viewing guide:

* Thursday, October 8: Skywatchers will see Venus pass 2.5° south of Leo’s brightest star Regulus with a cool crescent moon a little more than 3° to the west of the brilliant planet. If you live in Japan and the Far East, you’ll see a splendidly close conjunction of the moon and Venus at dawn on October 9, when the pair will be separated by a hair more than one moon diameter (0.6°). At nearly the same time, the moon will be in conjunction with Regulus.

Observers in Australia and New Zealand will see the Moon occult Venus in a dark sky sky before dawn (or in daylight, depending on exact location) on the 9th. Click HERE for information, times and a map for the event.

Ready to set the alarm again? The following morning, October 9, the moon makes a neat triangle with Jupiter and Mars. Source: Stellarium

* Friday, October 9: An even thinner moon passes about 3° north of Mars in the Americas at dawn and approximately 4° from Jupiter. Watch for the three luminaries to sketch a nifty triangle in the eastern sky 90 minutes to an hour before sunrise. Venus will gaze down at the planetary conclave 10° further west.

If you follow the moon to through its eastern descent, you'll be rewarded on Saturday morning (Oct. 11) with a fine pairing with Mercury. To see this conjunction, find a place with a good eastern horizon and bring binoculars to help you find the planet in bright twilight. Source: Stellarium — There’s not much of the Moon left by Saturday morning the 11th. The knife-edge crescent will hang less than a degree below the planet Mercury 40 minutes before sunrise. Make sure you find a spot with a good eastern horizon. Source: Stellarium

* Sunday, October 11: Mercury, which has quietly taken up residence again in the dawn sky, hovers 0.8° above a hair-thin moon this morning at 6 a.m. CDT. Best views will be about 45 minutes before sunrise, when the pair rises high enough to clear distant trees. Bring binoculars to help you spot the planet.

Mars and Jupiter 0.4 degree apart just before the start of dawn October 17 CDT. Venus won't be far away. Source: Stellarium — After a short break, Mars and Jupiter will cozy up 0.4 degree apart just before the start of dawn on October 17 CDT. Venus won’t be far away. Source: Stellarium

You’re thinking, why does this all have to happen in the morning? Thankfully, sunrise occurs around 7 a.m. for many locations, so you can see all these cool happenings in twilight around 6 a.m. — not terribly unreasonable. And now that the The Martian has finally hit the movie theaters, what better time to see the planet in the flesh? By pure coincidence, the location of stranded astronaut Mark Watney in the fictional account — Acidalia Planitia (Mare Acidalium) — will be facing dawn risers across the Americas and Hawaii this week.

October wraps up with a close grouping of three planets before dawn. This is the closest gathering of three planets since May 27, 2013. The next won't happen till January 10, 2021. Source: Stellarium — October wraps up with a tight trio of three planets before dawn. It will be the closest gathering of three planets since May 27, 2013. The next won’t happen till January 10, 2021. Source: Stellarium

Dare I say this string of continuous conjunctions is only a warm-up for more to come? Earth’s revolution around the Sun quickly brings Jupiter higher in the eastern sky, while Mars races eastward as if on a collision course. The following Saturday on October 17, the two will meet in conjunction less than 1/2 degree (one Full Moon width) apart. Very nice!

But it gets even better. On Tuesday morning, October 27, you’ll see all three planets huddle at dawn. One degree will separate Jupiter and Venus with Mars bringing up the rear several degrees further east. Feast on the view because there won’t be a more compact arrangement of three planets again until January 10, 2021.

October 6, 2015December 23, 2015 by David Dickinson

Comet US10 Catalina: Our Guide to Act II

Itching for some cometary action? After a fine winter’s performance from Comet C/2014 Q2 Lovejoy, 2015 has seen a dearth of good northern hemisphere comets. That’s about to change, however, as Comet C/2013 US10 Catalina joins the planetary lineup currently gracing the dawn sky in early November. Currently located in the constellation Centaurus and shining at magnitude +6, Comet US10 Catalina has already put on a fine show for southern hemisphere observers over the last few months during Act I.

Currently buried in the dusk sky, Comet US10 Catalina is bashful right now, as it shares nearly the same right ascension with the Sun over the next few weeks, passing just eight degrees from our nearest star as seen from our Earthly vantage point on November 7^th — and perhaps passing juuusst inside of the field of view for SOHO’s LASCO C3 camera — and into the dawn sky.

The hunt is on come early November, as Comet US 10 Catalina vaults into the dawn sky. From 30 degrees north latitude here in Central Florida, the comet breaks 10 degrees elevation an hour prior to local sunrise right around November 20^th. This should see the comet peaking in brightness right around magnitude +5 near perihelion the same week on November 16^th.

The angle of the comet’s orbit is favorable for northern hemisphere viewers in mid-November, as viewers start getting good looks in the early morning from latitude 30 degrees northward and the comet gains about a degree of elevation per day. This will bring it up out of the murk of twilight and into binocular view.

Mark your calendar for the morning of December 7^th, as the crescent Moon, Venus and a (hopefully!) +5 magnitude comet US10 Catalina will all fit within a five degree circle.

Here are some key dates with celestial destiny for Comet US10 Catalina for the remainder of 2015:

October

20-Crosses into the constellation Hydra.

November

2-Crosses into the constellation Libra.

16-Crosses into the constellation Virgo.

16-Reaches perihelion at 0.823 AU (127.6 million kilometers) from Sun.

26-Crosses the ecliptic plane northward.

27-Passes less than one degree from the +4.5 magnitude star Lambda Virginis.

December

7-Fits inside a five degree circle with Venus and the waning crescent Moon.

8-Passes less than one degree from the +4 magnitude star Syrma (Iota Virginis).

17-Crosses the celestial equator northward.

24-Crosses into the constellation Boötes.

In January, Comet US10 Catalina starts the New Year passing less than a degree from the -0.05 magnitude star Arcturus. From there, the comet may drop below +6 magnitude and naked eye visibility by mid-month, just prior to its closest approach to the Earth at 0.725 AU (112.3 million kilometers) on January 17^th. By February 1^st, the comet may drop below +10^th magnitude and binocular visibility, into the sole visual domain of large light bucket telescopes under dark skies.

Or not. Comets and predictions of comet brightness are always notoriously fickle, and rely mainly on just how the comet performs near perihelion. Then there’s twilight extinction to contend with, and the fact that the precious magnitude of the comet is diffused over its extended surface area, often causing the comet to appear fainter visually than the quoted magnitude.

But do not despair. Comets frequently under-perform pre-perihelion passage, only to put on brilliant shows after. Astronomers discovered Comet US10 Catalina on Halloween 2013 from the Catalina Sky Survey based just outside of Tucson, Arizona. On a several million year orbit, all indications are that Comet US10 Catalina is a dynamically new Oort Cloud visitor and will probably get ejected from the solar system after this all-too brief fling with the Sun. Its max velocity at perihelion will be 46.4 kilometers per second, three times faster than the New Horizons spacecraft currently on an escape trajectory out of the solar system.

The odd ‘US10’ designation comes from the comet’s initial identification as an asteroidal object, later upgraded to cometary status. The comet’s high orbital inclination of 149 degrees assured two separate showings, as the comet approached the Sun as seen from the Earth’s southern hemisphere, only to then vault up over the northern hemisphere post-perihelion. As is often the case, the comet was closest to the Sun at exactly the wrong time: had perihelion occurred around May, the comet would’ve passed the Earth just 0.17 AU (15.8 million miles or 26.3 million kilometers) distant! That might’ve placed the comet in the negative magnitudes and perhaps earned it the title of ‘the Great Comet of 2015…’

But such was not to be.

Ah, but the next ‘big one’ could come at any time. In 2016, we’re tracking comet C/2013 X1 PanSTARRS, which will ‘perhaps’ become a fine binocular comet next summer…

More to come. Perhaps we’ll draft up an Act III for US10 Catalina in early January if it’s a top performer.

October 5, 2015December 23, 2015 by Bob King

Why Was September’s Lunar Eclipse So Dark?

The September 17, 2015 total lunar eclipse - the last of the recent tetrad of lunar eclipses over the past 17 months - was darker than expected. Several factors described below were in play. This photo was taken in Washington's Olympic National Park. Credit: Rick Klawitter

First off, a huge thank you to everyone who made and sent their Danjon scale estimate of the totally-eclipsed Moon’s brightness to Dr. Richard Keen, University of Colorado atmospheric scientist. Your data were crucial to his study of how aerosols in Earth’s atmosphere and other factors influence the Moon’s appearance.

Grateful for your help, Keen received a total of 28 observations from 7 different countries.

Graphs created by Dr. Richard Keen plotting Danjon L values submitted by Universe Today readers and others that compare expected values (top curve) with observed values. The Moon was about half as bright during totality as expected with L=1.9. Credit: Dr. Richard A. Keen — Graph created by Dr. Richard Keen plotting Danjon L values submitted by Universe Today readers and others that compare predicted values (top curve) with observed values. The Moon was about half as bright during totality as expected with L=1.9. Credit: Dr. Richard A. Keen

Using the Danjon information and estimates of the Moon’s brightness using the reverse binocular method, Keen crunched the data and concluded that the Moon was about 0.6 L (Danjon) units darker than expected and 0.4 magnitude dimmer, a brightness reduction of 33%. This agrees well with my own observation and possibly yours, too. No wonder so many stars sparkled near the Moon that night.

Depending on how clear the atmosphere is, the Moon's color can vary dramatically from one eclipse to another. The numbers, called the Danjon Scale, will help you estimate the color of Sunday night's eclipse. Credit: Bob King — Lunar eclipse brightness is rated on the Danjon scale where “0” equals a dark gray totality and “4” a bright, coppery yellow. Credit: Bob King

I think it’s safe to say, most of us expected a normal or even bright totality. So why was it dark? Several factors were at play — one to do with the Moon’s location in Earth’s shadow, the other with a volcanic eruption and a third with long-term, manmade pollution.

During a perigee eclipse, the moon passes more deeply into Earth’s shadow compared to one that happens near apogee, when the moon is most distant from Earth. Moon distances not to scale and for illustration only. Credit: Bob King — During a perigean eclipse, the Moon passes more deeply into Earth’s shadow compared to one that happens near apogee, when the moon is most distant from Earth. Moon distances not to scale and for illustration only. Credit: Bob King

You’ll recall that the eclipse occurred during lunar perigee, when the Moon swings closest to Earth in its 27-day orbit. Being closer, it also tracked deeper into Earth’s umbra or inner shadow which narrows the farther back of the planet it goes. An apogean Moon (farthest from Earth) passes through a more tapered cone of darkness closer to the penumbra, where sunlight mixes with shadow. A Moon nearer Earth would find the umbral shadow roomier with the light-leaking penumbra further off in the distance.

Around midday on April 24, 2015, the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite acquired this natural-color image of the ash and gas plume from Calbuco volcano in southern Chile. Credit: NASA — On April 24, 2015, NASA’s Terra satellite acquired this photo of the ash and gas plume from Calbuco volcano in southern Chile. Credit: NASA

But there’s more. Working independently, Steve Albers of NOAA and Brazilian astronomer Helio Vital suggested another reason: aerosols in the atmosphere. “Earth’s stratosphere is no longer completely clean of volcanic ashes,” said Vital in an e-mail communication. “In fact, lingering aerosols (ash, dust, sulfuric acid droplets) from the explosion of Calbuco five months ago may be to blame for that excessive darkening.”

With the lunar horizon in the foreground, the Earth passes in front of the Sun on September 27, 2015 in this simulation, revealing the red ring of sunrises and sunsets along the limb of the planet responsible for illuminating the Moon during the eclipse. The clarity of the stratosphere at eclipse time can greatly affect lunar brightness during totality. The Earth and Sun are in Virgo for observers on the Moon with the bright star Beta Virginis at top. Click to see the video. Credit: NASA's Scientific Visualization Studio — With the lunar horizon in the foreground, the Earth passes in front of the Sun on September 27, 2015 in this simulation, revealing the red ring of sunrises and sunsets along the limb of the planet responsible for illuminating the Moon during the eclipse. The clarity of the stratosphere at eclipse time can greatly affect lunar brightness during totality. The Earth and Sun are in Virgo for observers on the Moon with the bright star Beta Virginis at top. Click to see the video. Credit: NASA’s Scientific Visualization Studio

While much of the debris blasted into the stratosphere made for colorful sunsets in the southern hemisphere, some of that material has likely made its way to the northern hemisphere. Albers has noticed an increase in yellow and purple sunsets in his home town of Boulder in recent months, telltale signs of volcanic spew at play.

Forest fires that raged across the western states and Canadian provinces all spring and summer may also have contributed. Most of that smoke usually stays in the lower part of the atmosphere, but some may have found its way to the stratosphere, the very layer responsible for transmitting most of the sunlight that falls into Earth’s shadow and colors the moon.

Graph showing magnitude estimates of the Moon's brightness during totality using the reverse binocular method. The predicted magnitude was -1.7 (a little brighter than Sirius) vs. the observed -1.3. Credit: Dr. Richard A. Keen — Graph showing magnitude estimates of the Moon’s brightness during totality using the reverse binocular method. The predicted magnitude was -1.7 (a little brighter than Sirius) vs. the observed -1.3. Credit: Dr. Richard A. Keen

Sunlight has to pass through these light-absorbing minerals and chemicals on its way through the atmosphere and into Earth’s shadow. Less light means a darker moon during total eclipse. Coincidentally, much of the totally eclipsed Moon passed through the southern half of the umbra which “increased the effectiveness of the Calbuco aerosols (which are still more concentrated in the southern hemisphere than the northern) at dimming the light within the umbra,” writes Keen.

Oceanus Procellarum and Mare Imbrium are large, dark volcanic plains that contributed to the Moon's faintness and dark-hued totality. Credit: Bob King — Oceanus Procellarum and Mare Imbrium are large, dark volcanic plains that contributed to the Moon’s faintness and dark-hued totality. Credit: Bob King

It also so happened that the darkest part of the moon coincided with two vast, dark volcanic plains called Oceanus Procellarum (Ocean of Storms) and Mare Imbrium, artificially enhancing the overall gloom over the northern half of the Moon.

U.S. satellite-derived map of PM2.5 averaged over 2001-2006. Credit: Dalhousie University, Aaron van Donkelaar — U.S. satellite-derived map of PM2.5 (fine particulate matter which includes sulfates and soot) averaged over 2001-2006. Credit: Dalhousie University, Aaron van Donkelaar

Finally, the human hand may also have played a role in lunar color and brightness. The burning of coal and oil has caused a gradual increase in the amount of human-made sulfate aerosols in the atmosphere since the start of the industrial revolution. According to NASA, at current production levels, human-made sulfate aerosols are believed to outweigh the naturally produced sulfate aerosols. No surprise that the concentration of aerosols is highest in the northern hemisphere where most industrial activity is found.

Isn’t it fascinating that one blood-red Moon can tell us so much about the air we breathe? Thank you again for your participation!

October 4, 2015December 23, 2015 by Bob King

Invest a Night in Vesta

The planetoid Vesta, which was studied by the Dawn probe between July 2011 and September 2012. Credit: NASA

The brightest asteroid visible from Earth prowls across Cetus the Whale this month. Vesta shines at magnitude +6.3, right at the naked eye limit for observers with pristine skies, but easily coaxed into view with any pair of binoculars. With the moon now gone from the evening sky, you can start your search tonight.

4 Vesta - its formal designation as the fourth asteroid discovered - travels along a short arc just south of the easily-found star Iota Ceti this month. Use this map to help you find Deneb Kaitos, Cetus' brightest star, and from their to Iota Ceti and Vesta. Source: Stellarium — Facing southeast around 10 p.m. local time in early October. 4 Vesta — its formal designation as the fourth asteroid discovered — travels along a short arc south of the easily-found star, Iota Ceti. Shoot a line from the Square of Pegasus south to arrive at Deneb Kaitos, Cetus’ brightest star, and from their to Iota Ceti and Vesta. Detailed map below. Source: Stellarium

Vesta came to opposition on September 28 and remains well-placed for viewing through early winter. Today’s it’s 134 million miles (225 million km) from Earth or about 5 million miles farther the Mars’ average distance from us. Although it’s one of the largest asteroids in the inner asteroid belt between Mars and Jupiter with a diameter of 326 miles (525 km), it never appears larger than a point of light even in many professional telescopes. Your binocular view will be as satisfying as the one through Mt. Palomar.

A spectacular central peak more than 14 miles high rises from the 310-mile-wide crater Rheasilvia. Credit: NASA — Like an inverted belly button, a spectacular central peak more than 14 miles high rises from the 310-mile-wide crater Rheasilvia. Credit: NASA

Discovered by the German astronomer Heinrich Olbers in March 1807, Vesta was named for the Roman goddess of home and hearth. NASA’s Dawn spacecraft, currently in orbit around another asteroid, Ceres, visited Vesta between July 2011 and September 2012, taking thousands of close-up images and measuring the mineral make-up of its soil and crust. We learned a few things while we were there:

Vesta is differentiated into crust, mantle and core just like the bigger planets are. That’s why you’ll sometimes hear it described as a “protoplanet”, the first of its kind discovered in our solar system.
A class of igneous meteorites fallen to Earth called Howardites, eucrites and diogenites (HED-meteorites) were confirmed as actual pieces of the asteroid that found their way here after being blasted into space by impact.
Some of the meteorites / rocks that pelted the asteroid from elsewhere in the solar system are water-rich.
Vesta’s covered in craters like the moon
A staggering-large 310-mile-wide (500 km) impact crater named Rheasilvia marks its south pole. The basin’s central peak rises to 14.3 miles (23 km), more than twice the height of Mt. Everest.
Gullies found on its surface suggest ancient water flows.

Cornelia Crater on the large asteroid Vesta. The crater is about 4 to 5 million years old. On the right is an inset image showing an example of curved gullies, indicated by the short white arrows, and a fan-shaped deposit, indicated by long white arrows. The inset image is about 0.62 miles (1 kilometer) wide. — Cornelia Crater on the asteroid Vesta. The crater is about 4 to 5 million years old. On the right is an inset image showing an example of curved gullies that may have been carved by water, indicated by the short white arrows, and a fan-shaped deposit, indicated by long white arrows. The inset image is about 0.62 miles (1 km) wide. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

You can see it all in your mind’s eye the next clear night. For skywatchers at mid-northern latitudes, Vesta climbs into good view around 10 o’clock in early October and 8 o’clock by month’s end. If you’re familiar with gangly Cetus, you can start with the 2nd magnitude star Deneb Kaitos, the brightest star in the constellation. If not, begin your Vestan voyage from the Great Square in Pegasus, high in the southeastern sky.

Once you've arrived at Deneb Kaitos, locate Iota Ceti, 10 degrees to the northwest. The star makes finding Vesta easy in binoculars this month. Source: Chris Marriott's SkyMap software — Once you’ve arrived at Deneb Kaitos, locate Iota Ceti, 10 degrees to the northwest. The star makes finding Vesta easy in binoculars this month. Stars shown to magnitude +7. North is up and the asteroid’s position is marked every 5 days at 10 p.m. Vesta fades slowly during the month to mag. 6.8 by Nov. 1. CDT. Source: Chris Marriott’s SkyMap software

Drop a line through the two stars along the left side of the Square and continue it down toward the southern horizon. You’ll run right into DK. Now elevate your gaze — or aim your binoculars — one outstretched fist (10°) or about two binocular fields of view above and right of Deneb Kaitos to find Iota Ceti (mag. 3.6).

Once you’ve got Iota, the asteroid will be in your field of view close by. Use the detailed chart to pinpoint its location with respect to Iota. Easy, right? Well, I hope so. Bon voyage to Vesta!

October 1, 2015December 23, 2015 by Bob King

New Nova Flares in Sagittarius – How to See it in Your Scope

The new nova in Sagittarius is located just above the Spout in the Teapot and shines at about magnitude +9 this week - visible in a small telescope. Credit: Bob King

A nova farmer would do well in the fields of Sagittarius. Four nights ago on September 27, Japanese amateur Koichi Itagaki plucked another “new star” from its starry furrows, the third nova discovered there this year!

For a few days, it was informally called Nova Sagittarii #3, but today received the official title of V5669 Sagittarii. Like the others, this one’s bright enough to see in a small telescope.

Itagaki first recorded it in his patrol camera at magnitude +9.5. The universe conceals so many of its greatest conflagrations as points of light that go from faint to bright. Novae are no exception. Such is the amateur observer’s lot. We need bring a mental picture, knowledge and a bit of imagination to the table to appreciate this bits of light that go boom in the night.

Use this wide finder map of Sagittarius to get a general idea of the nova's location. Lucky for us, it's in the same low power field of view of the pretty cluster-dark nebula combo NGC 6520 and Barnard 86, the so-called Inkspot Nebula. Source: Stellarium — Use this wide finder map of Sagittarius to get a general idea of the nova’s location. Lucky for us, it’s in the same low power field of view of the pretty cluster-dark nebula combo NGC 6520 and Barnard 86, the Inkspot Nebula. Source: Stellarium

Novae occur in binary star systems where a tiny but gravitationally-powerful white dwarf star pulls gases from a close companion star. The material piles up in a thin layer on the dwarf’s hot surface, fuses and burns explosively in a brilliant display of light. Suddenly, a star that may have been 15th or 20th magnitude flares brightly enough to see in a Walmart telescope.

Nova illustration with an expanding cloud of debris surrounding central fireball emitting red hydrogen-alpha light.

October’s not exactly prime time for viewing Sagittarius for mid-northern observers. By late evening twilight, it’s already in low in the southwestern sky. But if you can find an opening in that direction or if you’re lucky enough to have a 15-minute-wide gap between the trees like I do, you can spot this sucker. I set up my scope shortly before 8 o’clock or about an hour after sundown. Western Sagittarius remains in reasonably good view for about another hour.

Start at the Gamma Sagittarii and star hop from there to Gamma 1 and then north to the small star cluster NGC 6520 and adjacent dark nebula Barnard 86. You may not see the nebula because of atmospheric extinction at low altitude, but the cluster stands out well. A magnitude 7 star lies along its northwestern edge, and the nova is just 1/2 degree from there. If you have a go-to scope, its celestial coordinates are: R.A. 18 hours 3.5 minutes, Dec. -28 degrees 16 minutes.

AAVSO chart showing the location of V5669 Sgr. North is up. I've added the star cluster NGC 6520 and Barnard 86. To make your own charts of the nova and its neighborhood, go to aavso.org, type in the star's name and select "Create a finder chart". — AAVSO chart showing the location of V5669 Sgr. North is up. I’ve added the star cluster NGC 6520 and Barnard 86. To create your own customized charts of the nova, go to aavso.org, type in the star’s name and select “Create a finder chart”. Credit: American Assn. of Variable Star Observers (AAVSO)

To precisely pinpoint the nova, use the AAVSO chart, which also includes comparison stars with their magnitudes labeled (but without the decimal point). Do you notice any color? Photos show it as pale red from the emission of hydrogen-alpha light in the deep red of the visual spectrum. Novae often emit H-alpha especially in their early, hot “fireball” stage as gases are rapidly expanding from the explosion into space.

The pretty star cluster NGC 6520 and Ink Spot Nebula Barnard 86. The cross shows the location of the nova. Credit: Johannes Schedler / panther-observatory.com — The pretty star cluster NGC 6520 and Ink Spot Nebula Barnard 86. The cross shows the location of the nova. The star field may look intimidating, but this time exposure photo reveals minions more than are visible in an amateur telescope. Credit: Johannes Schedler / **panther-observatory.com**

No telling what the star will do in the coming days. That’s what makes novae and variable stars in general so much fun to watch. I caught the star Monday night September 28 at magnitude +8.6. The following night it dropped to 9.3 and then edged back up to 9.2 last night. Astronomers study these fluctuations to understand a nova’s behavior and evolution. I can’t wait to see what it’s doing tonight.

One thing I really like about this nova is its location so near a pretty pair of deep sky objects. On your way to this amazing pinprick of light, stop by the cluster and dark nebula for a final farewell to the summer season.

September 29, 2015April 26, 2016 by David Dickinson

Challenge-Watch the Daytime Moon Occult Aldebaran for North America This Friday

How about that total lunar eclipse this past Sunday? Keep an eye of the waning gibbous Moon this week, as it begins a dramatic dive across the ecliptic towards a series of photogenic conjunctions throughout October.

The Main Event: This week’s highlight is an occultation of the bright +0.9 magnitude star Aldebaran (Alpha Tauri) by the waning gibbous Moon on Friday morning October 2^nd.

The occultation footprint for Friday’s occultation of Aldebaran by the Moon, with pre-dawn, dawn and post-dawn zones annotated. Image credit: Occult 4.0 software

This occurs in the pre-dawn hours for Alaskan residents, and under favorable dawn twilight skies along the U.S. and Canadian Pacific west coast; the remainder of the contiguous United States and Canada will see the occultation transpire after sunrise. This is the 10th of 49 occultations of Aldebaran by the Moon worldwide running from January 29th, 2015 through September 3rd, 2018. The Moon will be at 74% waning gibbous phase, and Aldebaran will disappear behind its illuminated limb to reappear from behind its trailing dark limb.

Check out this amazing Vine of the last occultation of Aldebaran by the Moon courtesy of Andrew Symes @FailedProtostar:

It’s interesting to note that the southern graze-line for the occultation roughly follows the U.S./Mexican border. Seeing a bright star wink in and out from behind the lunar valleys can be an unforgettable sight, adding an eerie 3D perspective to the view. A detailed analysis of the event can even help model the rugged limb of the Moon.

Hunting stars and planets in the daytime can be an interesting feat of visual athletics. We’ve managed to spy Aldebaran near the lunar limb with binoculars during an occultation witnessed from Alaska on September 4^th, 1996, and can attest that it’s quite possible to see a +1^st magnitude star near the Moon with optical aid. A clear blue sky is key. The Greek philosopher Thales noted that stars could be seen from the bottom of a well (though perhaps he’d fallen down a well or two too many in his time)… Friday’s event should push your local seeing to its limits. Start tracking Aldebaran before local sunrise, and you should be able to follow it all the way to the lunar limb, clear skies willing.

The occultation path for various locales across the United States Friday morning. Image credit: Dave Dickinson/Stellarium

Here’s a listing of times for key events for Friday from around the U.S. Check out The International Occultation Timing Association’s page for the event for an extensive listing:

Key times for the occultation for the same locales depicted in the graphic above, along with the lunar elevation (altitude) above the local horizon at the time noted. Image credit: Dave Dickinson

And whenever the Moon meets Aldebaran, it has to cross the open star cluster of the Hyades to get there, meaning there’ll be many other worthy occultations of moderately bright stars around October 2^nd as well. Gamma Tauri, 75 Tauri, Theta^1 Tauri, and SAO93975 are all occulted by the Moon on the morning of October 2^nd leading up to the Aldebaran occultation; particularly intriguing is the grazing occultation of +5 magnitude 75 Tauri across the Florida peninsula.

The path of the moon through the Hyades this weekend. Image credit: Starry Night Education software — The path of the Moon through the Hyades this weekend. Image credit: Starry Night Education software

Fun fact: the Moon can, on occasion, occult members of the M45 Pleiades star cluster as well, as last occurred in 2010, and will next occur on 2023.

Chasing the Moon through October

Follow that Moon for the following dates with astronomical destiny worldwide:

The Moon reaches Last Quarter phase on Sunday, October 4th at 21:06 UT/5:06 PM EDT.
A close pass with Venus on October 8^th, with a brilliant occultation visible in the pre-dawn hours from Australia.
A tight photogenic grouping of the Moon, Mars and Jupiter in a four degree circle on the morning on October 9^th;
A close pass of the Moon just 36 hours from New near Mercury on the morning of Sunday, October 11^th, with another occultation of the planet visible from Chile at dawn;
And finally, New Moon (sans eclipse, this time) occurring at 00:06 UT on October 13^th, marking the start of lunation 1148.

Why occultations? Consider the wow factor; light from Aldebaran left about 65 years ago, before the start of the Space Age, only to get ‘photobombed’ by the occulting Moon at the last moment. Four bright stars (Regulus, Spica, Antares and Aldebaran) lie along the Moon’s path in our current epoch. Dial the celestial scene back about two millennia ago, and the Moon was also capable of occulting the bright star Pollux in the astronomical constellation of Gemini as well.

We’ll be running video for the event clear skies willing Friday morning here from Hudson, Florida in the Tampa Bay area. And as always, let us know of your tales of astronomical tribulation and triumph!

September 27, 2015December 23, 2015 by Bob King

How to (Hopefully) Find Clear Skies for Tonight’s Total Lunar Eclipse

Weather looking a bit iffy tonight? Using the resources described below, you just might be able to escape the clouds. Credit: Bob King

We’ve arrived at eclipse day, so now the big question is, will it be clear? My favorite forecast for major astronomical events reads something like this: Fair skies tonight with light winds and lows in the middle 50s.While I hope that’s exactly what’s predicted for your town, in my corner of the world we’re expecting “increasing clouds with a chance for thunderstorms”.

That’s just not nice. Same by you? Here’s how to find that clear spot if you’re facing bad weather tonight.

One of my favorite cloud-checking sites is the GOES East view of the U.S., Canada and Central America taken from geostationary orbit. Credit: NASA — One of my favorite cloud-checking sites is the GOES East view of the U.S., Canada and Central America taken from geostationary orbit. This map shows the scene at 10:45 a.m. CDT this morning. Credit: NASA

I usually check the GOES (Geostationary Operational Environmental Satellite) images that weather forecasters use to display and animate the movement of clouds and weather fronts during the nightly newscasts. Once I know the location and general drift of the clouds, I get in a car and drive to where it’s likely to either remain or become clear. Depending on the “magnitude” of the event I might drive 50 to 150 miles. If nothing else, doing astronomy guarantees many adventures.

GOES West view of the western U.S., Canada and Hawaii taken at 11 a.m. CDT. Credit: NASA

You’ll find these most helpful images at either the GOES East site, which features a photo of the entire mainland U.S., Central America and much of Canada, updated every 15 minutes. Since the satellite taking the photos is centered over the 75° west parallel of longitude, its focus is primarily the eastern two-thirds of the U.S. and Canada. For the western U.S., western Canada and Hawaii, head over to the GOES West site.

After you set the width and height to maximum values, you'll get a picture like this which was taken at 11 a.m. CDT and features the upper and lower Midwest. Credit: NASA — After you set the width and height to maximum values, you’ll get a picture like this, taken at 11 a.m. CDT. Credit: NASA

Once there, you’ll be presented with a big picture view of the U.S., etc., but you can click anywhere on the map for a zoomed-in look at a particular region. Before you do, set the “width” and “height” boxes to their maximum values of 1400 (width) and 1000 (height). That way you’ll get a full-screen, nifty, 1-kilometer image when you go in close. All images have a time stamp in the upper left corner given in Universal or Greenwich Mean Time (GMT). Subtract 4 hours to convert to Easter Daylight; 5 for CDT; 6 for MDT and 7 for PDT.

You can check back all day long for fresh photos and watch the march of the clouds over time. Or you can have the site assemble up to 30 of the most recent images into an animation loop and watch it as a movie. Combing current photos, the animation and your local forecast will inform your plans about whether to remain at home to watch the eclipse or get the heck out of town.

Infrared image of the east-central U.S. at 11 a.m. CDT today. Credit: NASA — Infrared image of the east-central U.S. at 11 a.m. CDT today. Clouds can be seen and tracked at night using the infrared channel on the GOES East and West sites. Credit: NASA

When night arrives, you can still get a reasonably good idea of where the clouds are and aren’t by clicking on the infrared channel link at the top of the site. I also like to use the NCAR (National Center for Atmospheric Research Real-Time Weather Data) site. They offer a black and white infrared option that provides a clearer picture. At the site, select your “channel” then click on one of the regional acronyms on the interactive U.S. map.

So far, we’ve been talking about the weather in real time. When it comes to forecasts, one of the most useful tools of all and a true godsend to amateur astronomers is Attilla Danko’s ClearDarkSky site. Click on the Clear Sky Charts link to access interactive charts for thousands of locations across the U.S., Canada and parts of Mexico. For example, if you click on Illinois, you’ll get a list of sky conditions for 105 locations throughout the state. The Chicago link pops up six rows of data-packed squares with colors ranging from deep blue to white.

The cloud cover forecast for Chicago for the next day as depicted in Attilla Danko's Clear Dark Sky site. Copyright: Attilla Danko — The cloud cover forecast for Chicago today Sept. 27 through early Tuesday Sept. 29 as depicted in Attilla Danko’s Clear Dark Sky site. The forecasts can be sponsored for a donation by various groups or individuals. This one is by the Chicago Astronomical Society. Copyright: Attilla Danko

The first row indicates cloud clover with varying shades of blue representing the percentage of clear sky. Medium blue means partly cloudy; white indicates 100% overcast. Additional data sets include sky transparency, seeing conditions, hours of darkness, wind, temperature and humidity. While no forecast is 100% accurate, the reliability of the models Danko uses makes Clear Sky Charts one of best tools available for skywatchers. Want a real treat? If you click on one of the squares in the Cloud Cover row, a large image showing cloud cover at the time will pop up. You’ll also find another, more general interactive cloud forecast graphic at WeatherForYou.com.

Thanks to a helpful reader suggestion, I recently learned of Clear Outside, a forecasting site similar to Clear Sky Charts but worldwide. Be sure to check it out. Satellite imagery like the U.S. GOES East and West is available for European and African observers at Sat24.

So what does the U.S. look like for weather tonight? Mostly clear skies are expected from New York State up through Maine, across the center of the country, the desert Southwest and the Northwest. Expect partly cloudy conditions (with some mostly cloudy spots) for the Upper and central Midwest, and mostly cloudy to overcast skies in the southern and southeastern seaboard states.

But who knows? By using these sites, you might just improve your chances of seeing what promises to be a spectacular lunar eclipse tonight. Some of you reading this undoubtedly have your own favorite weather hangouts. Please share them with us in the comments section. The more the merrier!

As always, if you’re completely shut out, here are a few sites where you can watch it live on the Web:

Gianluca Masi’s Virtual Telescope starting at 9:45 p.m. CDT (2:45 UT)
Sky and Telescope webcast begins 8 p.m. CDT (1:00 UT)