January 22, 2020

Astro-Vid of the Week: An Amazing Grazing Occultation

Going, going…

Credit Stellarium

What a difference a few 100 meters can make. On the night of March 5th, 2017, the waxing crescent Moon occulted the bright star Aldebaran. This event was well placed for North American viewers… heck, it even occurred over the weekend on a Saturday night, to boot. We even managed to dodge social obligations to briefly duck outside with our trusty 15x 45 image-stablized binoculars to watch Aldebaran wink out behind the dark limb of the Moon.

The event was even more interesting up north, as the graze-line for the occultation crossed the northeastern United States and Canada. And the good folks at the North York Astronomical Association were at the ready to record the event.

But you’ve never seen an occultation like this. What follows is a synchronized video, showing the event from multiple locations:

Aldebaran Grazing Occultation March 5, 2017 Combined Videos from Andreas Gada on Vimeo.

You can see the marked timing difference for the disappearance and reappearance of Aldebaran, for even closely spaced stations. The audio was even true to the event: you can hear observers cry out as the star winks in and out! And all the while, the time hack provided by WWV radio out of Fort Collins plays on in the background.

What’s the big deal? Well, grazing occultations reveal something about the profile and the jagged edge of the lunar limb. Sometimes, undiscovered faint unseen companion star might even briefly reveal themselves as the blinding light of the primary is blocked by the Moon.

An amazing job, for sure. And for observers in Japan and NW Asia, the Moon occults Aldebaran again tomorrow on April 1st (no fooling!) This is occultation number 30 in a series of 49 for Aldebaran, running from January 29th, 2015 to September 3rd, 2018.

Don’t miss the next occultation, coming to a sky near you.


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