November Occultations of Aldebaran & Regulus

This November, the Moon occults two 1st-magnitude stars for much of North America just six days apart. The first occultation happens mostly in early-evening darkness. The second takes place in broad daylight — an extra challenge for the adventurous.

On July 25th, Shahrin Ahmad in Kuala Lumpur, Malaysia, took a telescopic video of Regulus emerging from behind the Moon's bright limb.

• Aldebaran, November 5th. The Moon will be just a trace past full and shining in the eastern sky around dinnertime when, for the eastern and central parts of the continent, its bright limb will creep up to and hide orange Aldebaran — a telescopic “fire on the Moon” in its final seconds. The star will reappear on the other side from behind the Moon’s very thin dark sector (Luna is only 5% unilluminated) up to an hour or more later.

The farther west you are, the earlier and lower it happens. From Texas through Montana, the star will already be behind the Moon at moonrise; you’ll only see the reappearance. Observers farther west miss out altogether

Northern Europeans will see the occultation at a later hour: around the middle of the night of November 5–6.

• Regulus, November 11th. The following Saturday, telescope users from Georgia through British Columbia and points father south and west can try for the Moon occulting blue-white Regulus high in a (hopefully) blue sky. The Moon will be a day past last quarter. Again the star disappears on the bright limb and reappears on the dark limb, which will be invisible in the daytime blue. Good luck.

Complete timetables for both stars’ occultations for hundreds of cities and towns are available from the The International Occultation Timing Association. Pay attention there to the altitudes listed for the Sun and Moon. The daytime sky around the Moon is deeper blue when the Moon is higher than the Sun, giving your telescope the best chance. The “CA” column tells the cusp angle where the star disappears or reappears: how many degrees from the Moon’s north or south cusp the event occurs, so you’ll know exactly where to look. For each star, the prediction page displays three long tables with less-than-obvious divides: for the disappearance, the reappearance, and the locations of cities.

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