Lights Out: A Fine Occultation of Aldebaran Spans the Atlantic

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

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 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:

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.

Image credit and copyright: Rob Sparkes
Aldebaran on the ‘flip side’ post lunar occultation. Image credit and copyright: Rob Sparkes


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:

Image credit: Dave Dickinson
Aldebaran near the Moon pre- (left) and post- (right) sunset. Click to enlarge. Image credit: Dave Dickinson



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!