Catch ‘The Great American Occultation’ of Aldebaran Saturday Night

Ever watch the Moon cover up a star? There’s a great chance to see just such an event this coming weekend, when the waxing gibbous Moon occults (passes in front of) the bright star Aldebaran for much of North America.

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This Week: Occultations of Aldebaran, Regulus vs. the Supermoon

It’s a busy week for the Moon. While our large solitary natural satellite reaches Full and interferes with the 2016 Geminids, it’s also beginning a series of complex bright star occultations of Aldebaran and Regulus, giving us a taste of things to come in 2017. First up, here’s the lowdown on this week’s occultation of […]

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Watch the Moon Occult Vesta and Aldebaran This Weekend

The Moon occults Aldebaran last lunation on March 14th as seen from India. Image credit and copyright: Rajneesh Parashar

So, did you miss yesterday’s occultation of Venus by the Moon? It was a tough one, to be sure, as the footpath for the event crossed Europe and Asia in the daytime. Watch that Moon, though, as it crosses back into the evening sky later this week, and occults (passes in front of) the bright star Aldebaran for eastern North America and, for Hawaii-based observers, actually covers the brightest of the asteroids, 4 Vesta.

These events are all part of a cycle of occultations spanning 2016.

When we left off last week, the Moon was headed towards New, which occurs today at 11:25 UT, marking the start of lunation 1154. We did indeed manage to spy Venus juuuust off of the limb of the razor thin Moon from our current base camp in Jimena de la Frontera Spain at sunrise, less than 29 hours from New. Observers based in Hawaii should be able to spot the waxing crescent Moon without optical aid on the evening of April 7th, and North America and Europe will see the Moon return to the evening skies on the next evening at 32 and 38 hours old, respectively.

Follow that Moon

First stop: the Moon occults 4 Vesta for observers based in Hawaii at dusk, centered on 3:42 Universal Time (UT) on April 9th. The Moon is 4% illuminated, while 4 Vesta shines at magnitude +8. Notably, Vesta can reach magnitude +5, and is the only asteroid visible to the naked eye under dark skies as it nears opposition, as next occurs on January 18th, 2017. If you haven’t laid eyes on Vesta before with binoculars or a telescope, this weekend is a good time to try, using the nearby Moon as a guide. North America will see a close two degree pass on the same evening.

Key times for the event, in UT:


Ingress: 4:46 UT

Moon altitude: 24 degrees

Sunset: 4:48 UT

Next up, the Moon crosses the Hyades star cluster and meets Aldebaran on the evening of April 10th. This is the 4th occultation of Aldebaran of 13 by the Moon for 2016, and the 17th of 49 for the current cycle, running from January 2015 to September 2018. Aldebaran is the bright star that is most frequently visited by our Moon in the current epoch. The Moon can also occult Regulus, Spica and Antares, and the 18.6 year motion of its nodes as it intersects the ecliptic causes these cycles of occultations to change accordingly.

Easternmost Newfoundland will see the occultation transpire under dark skies, while the United States Eastern seaboard and the Canadian Maritimes will see the event under dusk skies. If you live west of this, do not despair. We’ve been able to easily spy Aldebaran in daytime skies, using binoculars and the nearby crescent Moon as a guide.

Here’s some key times for selected cities:

Gander, Newfoundland

Ingress: 23:13 UT

Moon altitude: 29 degrees

Sunset: 22:23 UT

Atlanta, Georgia

Ingress: 22:35 UT

Moon altitude: 62 degrees

Sunset: 00:05 UT

Boston, Massachusetts

Ingress: 22:53 UT

Moon altitude: 45 degrees

Sunset: 23:20 UT

Chicago, Illinois

Ingress: 22:25 UT

Moon altitude: 60 degrees

Sunset: 00:27 UT

Catching such an event is unforgettable, as a star winks abruptly out of existence along the dark leading edge of the waxing Moon. What you’re seeing is mainly a product of the motion of the Moon itself around the Earth.

The next occultation Aldebaran favors northwestern North America on May 19th, 2016, and the next occultation of a planet (Jupiter) by the Moon occurs on July 9th favoring the southern Indian Ocean region. And remember, even if you’re located outside of the ‘occultation zone,’ you can still witness a close pass Aldebaran and the Moon, as our large natural satellite carouses through the Hyades and occults numerous fainter stars for observers worldwide.

Why occultations? Well, lots can be discerned about both bodies during such an event. Remember, New Horizons used radio occultations as it flew through the ‘shadows’ of Charon and Pluto last summer, in an effort to measure its atmosphere. Likewise, the high-flying SOFIA observatory used an occultation of a star by Pluto to make backup confirming observations from Earth. A grazing occultation of a star by the Moon can help map the lunar limb, and an occultation of a star by an asteroid can actually help measure the rock’s size and shape. Unlike many astronomical events, occultations are quick enough to make great Vines or gifs, and Aldebaran is bright enough to capture with a tripod mounted video camera zoomed in on the Moon.

As always, let us know what you see, and send those pics and vids in to Universe Today!

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Watch the Moon Beat a Path Across the Hyades Tonight

Do you see it? The Moon closes in on Aldebaran last October. Image credit and copyright: Frank Tyrlik

Once more, unto the breech…” Ready to brave the February cold and the ongoing arctic polar express? Tonight, North American skywatchers will witness an encore event, as the waxing gibbous Moon crosses the Hyades star cluster and – for a lucky few — occults the bright star Aldebaran.

This occultation is number 15 in a current series of 36 of Aldebaran by the Moon, running from January 29th, 2015 to September 12th, 2017. The Moon occults the bright star once for every lunation in 2016, though the event is only visible across a narrow footprint along the surface of the Earth. Tonight’s occultation sees the ‘shadow of the Moon’ cast by +0.9 magnitude Aldebaran cross a wide arc of the northern Pacific. In the United States, the graze line runs from around Seattle Washington to Salt Lake City Utah, down to around Phoenix Arizona. The western U.S. will witness the occultation in the early morning hours centered around 8:00 UT/1:00 AM MST, while Japan and the Far East will catch the event before sunset. The Aleutian Islands will see a spectacular graze of Aldebaran along the limb of the 61% illuminated Moon, low towards the southern horizon.

The rest of North America will see the Moon closing in on Aldebaran this evening just before moonset around 1 AM local. But don’t despair, the Moon occults lots of fainter stars as it traverses the Hyades, including +4th magnitude Gamma Tauri and the +3rd magnitude stars Theta Tauri^1 and ^2. Though Aldebaran lies in the direction of the Hyades star cluster, it’s actually 42% closer to the Earth at 65 light years distant. You can find a listing of timings for the ingress and egress for tonight’s event for selected major cities along the U.S. West Coast on the International Occultation Timing Association’s (IOTA) site for the event

IOTA North American coordinator Brad Timerson just released a video compilation for the January 20th occultation of Aldebaran by the Moon:

In the current epoch, four bright stars lie in the path of the Moon: Regulus, Spica, Antares and Aldebaran. About two centuries ago, the Moon could also occult Pollux in the constellation Gemini as well. Lying about five degrees south of the ecliptic, the Moon frequently visits Aldebaran and the Hyades on ‘shallow years’ such as 2015 into 2016. This is also known as a minor lunar standstill. Hillier years, such as 2025, will see the orbit of the Moon steeply inclined versus the ecliptic, allowing it to visit the Pleiades star cluster once again. Sometime thousands of years in the far future, the 26,000 year cycle known as the Precession of the Equinoxes will carry the Moon’s path away from Aldebaran, and farther in time still, back towards it again.

Aldebaran is most prominent during the ingress phase along the Moon’s leading dark limb. We even managed to see the star near the Moon with binoculars last month ten minutes before local sunset from Ormond Beach, Florida. The ‘wink out’ of a star during ingress is surprisingly swift, a rarity in astronomical observing, a pursuit where many events exceed mere human life spans.

Recording an occultation of a bright star by the Moon is as simple as coupling a video recorder to a telescope and recording the event at the appointed time. Aldebaran is bright enough to show up along the dark limb of the Moon even in a smartphone capture. Be sure to start setting up an hour or so early to get your tracking, focus and exposure settings right… just don’t drain those batteries out in the frigid air before showtime! The swiftness of an occultation also makes it a very appropriate event for that hip new short attention span platform, Vine.

As well as being the closest open cluster to our solar system, the Hyades also have another important distinction: the large common proper motion of its members allowed astronomer Lewis Boss to trace their relative motion back to a converging point in space, a key early measurement of local galactic motion made just over a century ago in 1908.

Tonight’s sky provides a good study in the motion of all things, near and far. A good reason to brave the chill!

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Lights Out: A Fine Occultation of Aldebaran Spans the Atlantic

The waxing gibbous Moon closes in on Aldebaran (lower left). Image credit and copyright: Sarah & Simon Fisher

They braved the cold, cursed the clouds, wrestled with frozen telescope focusers and more, as dedicated astros worked to catch the first occultation of the bright star Aldebaran for 2016 by the waxing gibbous Moon.

The event went down last night into the wee hours of the morning, and was visible across North America into western Europe and the United Kingdom.

We’re always amazed at the sorts of astro-images folks take of a given event, now shared in near real time across social media. Less than a decade ago, a bright star occultation by the Moon — especially one occurring in the depths of northern hemisphere winter — would have grabbed the interest of at most a handful of intrepid specialist observers. Last night’s occultation of Aldebaran created a flood of images and videos across Twitter, Instagram, Vine and more.

#Aldebaran after coming out. Look along the top right. #Astronomy #occultation #Moon

A video posted by Coy (@xt8dob) on Jan 19, 2016 at 6:53pm PST

Unlike other astronomical events that unfold over periods of time often longer than a human lifespan, occultations are nearly instantaneous affairs. Here’s a great close-in view of the Moon capturing the immediacy of the event courtesy of the Sheep Hill Astronomical Association  based in Boontown, New Jersey:

Many remarked on how quick the disappearance of Aldebaran along the dark limb of the Moon was. You can easily see the motion of the rotation of the Earth at the eyepiece if you turn the drive motor off, but during a lunar occultation, you’re seeing the motion of the Moon itself as it plows over the target star or planet.

The abrupt nature of occultations make them worthy of the modern day ‘short attention span theater’ ideal for a 6.5 second long Vine.

Observing from Canada, IPhone astrophotographer Andrew Symes (@FailedProtostar) caught the ingress of Aldebaran along the dark limb of the Moon:

And then, caught the egress just over an hour later, as the star exited along the bright limb of the waxing gibbous Moon:

Many observers across North America battled clouds and bone-chilling January temperatures to witness the event. Though the occultation occurred during prime time evening hours for North America, observers in the United Kingdom had to contend with a very low altitude Moon in the early AM hours.

I’m standing out in 18 degree weather for this? #moon #occultation (Aldebaran is at 3:00)

— Drunken Astronomer (@Corlykins) January 20, 2016

I particularly like how you can see the motion of the Moon briefly in many of the videos. Aldebaran does indeed have a very tiny apparent angular diameter of about 45 mas (that’s milliarcseconds) as seen from the Earth, too small to measure during an occultation. Lots more folks are also coupling smartphones to their telescopes these days, with amazing results:

“It’s gone” Occultation of Aldebaran. iPhone through @Celestron 8″ SCT Williamsburg VA @EpicCosmos @Astroguyz

— Christopher Becke (@BeckePhysics) January 20, 2016

As always, trick shots abound. We very nearly had an aircraft transit the Moon observing from here in Ormond Beach, Florida as it photobombed the scene. One enterprising individual even flew a drone during the event, a difficult feat when you imagine how tough it must have been to stabilize the flyer along the light of sight with the Moon…

As we write this, video from the crucial graze line along the southern United States into northern Mexico has yet to surface. Brad Timerson at the International Occultation Timing Association  notes that the 81% illuminated waxing gibbous phase of the Moon, plus fickle weather conditions made capture of a grazing occultation difficult, but we’ll drop one in if it surfaces. A brief search YouTube reveals a paucity of good lunar grazing vids, suggesting a capture of such an event is rarer than blurry pics of Bigfoot…

And as with occultations, eclipses and other astronomical events involving things passing in front of each other, the question after the finale is: when’s the next one? Well, last night’s occultation of Aldebaran by the Moon was the first of 13 for 2016 — one for each lunation — but it was the best placed for North America. There is, however, a decent one for northern western United States and western Canada next month on the morning of February 16th.


Alas, last night found us in Florida, the only state in the ‘lower 48’ that sat out last night’s occultation. Hey, it was also the only state in the Union with temps above freezing, so we’ll take it. Our modest personal challenge was to spy Aldebaran in the daytime, a feat we once completed observing from North Pole, Alaska in the late 1990s.

Aldebaran was an easy catch with binocs two degrees from the Moon against deep blue skies 30 minutes prior to sunset, though we didn’t manage to nab it photographically until just minutes before:



And of course, a naked eye sighting of Aldebaran didn’t occur until about 10 minutes after sunset.

But such are the tales of astronomical tragedy and triumph. Hopefully, last night’s fine occultation whetted your appetite  to try for more!

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Watch the Moon Occult Aldebaran for Europe Wednesday Night

The Moon occults Aldebaran on October 30th, 2015. Image credit and copyright: Zalatko Orbanic

An early Christmas present is on tap this week for observers in Europe, the United Kingdom and northern Asia, as the waxing gibbous Moon occults (passes in front of) the bright star Aldebaran on the evening of Wednesday December 23rd.

The event will see the 87% illuminated Moon occulting the +0.8 magnitude star Aldebaran under dark skies on Wednesday evening December 23rd across Europe, the United Kingdom, northern  Africa and northern Asia. Initial ingress will occur across the slender dark limb of the waxing gibbous Moon, with egress against the bright illuminated limb. Usually, the brilliant Moon would wash out any star near Full, but Aldebaran should remain visible, even during egress.

The International Occultation Timing Association (IOTA) maintains a page listing local circumstances for towns and cities in the occultation path. This is the 13th and final occultation of Aldebaran for 2015 (one for each lunation), and the 13th in a series of 51 stretching from January 29th, 2015 to September 8th, 2018.

Clouded out? The Virtual Telescope Project is planning on broadcasting the occultation hosted by astronomer Gialuca Masi live starting at 17:45 UT.

Why observe occultations? From transits to eclipses to events such as this week’s involving the Moon, the chance alignment of celestial bodies often gives us a chance to discover something of their true nature. Close binary stars have been uncovered during occultations. Transits reveal exoplanets to platforms such as Kepler. Some stars exhibit a tiny angular diameter, apparent only during occultations. The passage of an asteroid in front of a star can reveal something of its shape and size. And in the case of bright star grazes along the lunar limb, such as passage can be used to map the Moon’s jagged edge in profile.

The southern limit graze line for Wednesday’s event runs right through central Turkey, from the southwest to the northeast.

Things passing in front of each other have even been used to pinpoint historical dates in time. Occultations of the Pleiades cited in Ptolemy’s time gave medieval astronomers some inkling that the stars and constellation patterns had shifted slightly during the intervening millennia.

Four bright stars lie along the Moon’s path in the current epoch: Antares, Regulus, Spica and Arcturus. Shining at magnitude +0.86, Aldebaran is the brightest star that the Moon can occult, beating out Antares and Spica by a tenth on a magnitude. Its even worth trying to spy Aldebaran near the limb of the Moon in the daytime, using binoculars under clear deep blue skies.


Fun Fact: until about 117 BC, the Moon could occult the bright star Pollux in the constellation Gemini. The Precession of the Equinoxes has since moved Pollux out of the path of the Moon, though it’ll rejoin the Moon’s occultation repertoire in the far future.

Aldebaran is also one of the most frequent hosts of the passage of the Moon, and when the Moon crosses the Head of Taurus the Bull as it does this week, it also crosses in front of the Hyades open star cluster as well, covering and unveiling several other stars along the way. Jean Meeus notes in his book Astronomical Tables that after the current cycle of occultations of Aldebaran wraps up in 2018, no bright +1st magnitude star will be occulted by the Moon until Antares August 25th, 2023. Occultations of Aldebaran won’t resume until August 18th, 2033.

Observing bright star occultations is easy: observers in Europe and Asia will see Aldebaran wink out Wednesday night with the unaided eye, though binoculars or a small telescope will certainly help. Recording occultations is fun and easy to do: we’ve been able to record events simply aiming a video camera afocally through the ‘scope. Running WWV radio in the background can give you a precise audio time hack during the event.

Watch that Moon, as Christmas 2015 sports a Full Moon occurring at 11:11 UT. A Christmas Full Moon last occurred in 1977, and won’t happen again until 2034. Even rarer is a total lunar eclipse on Christmas, which is due to happen once again in 2531 AD.

2016 will see 13 more occultations of Aldebaran by the Moon, as well as the first occultation of Regulus in a new cycle on December 18th. And although this week’s occultation will be over once the Moon rises for North America, the continent gets a similar event during the next lunation on January 20th, 2016.

More to come on the year in astronomy ahead. Don’t miss these exciting events, coming to a sky near you.

Intro image credit and copyright: Zalatko Orbanic

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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 […]