The “super” full moon of Nov. 13-14 was in fact the closest full moon since 1948. While the full moon of Dec. 13 is still referred to as a supermoon, it’s barely in the club.

The term “supermoon,” coined by astrologer Richard Nolle in the 1970s, refers to a full moon that occurs within 24 hours of perigee, which is that moment when the moon is closest to Earth in its monthly orbit. A moon is officially “full” when the sun, Earth and moon are in a straight line, with the Earth in between the two other celestial bodies. This December, the moon will be full at 2:06 p.m. Dec. 13. However, perigee occurs 25 hours earlier, at 1 p.m. Dec. 12.

So actually by the technical definition, this Dec. 13 full moon is outside of the club by one hour, since it occurs 25 hours after perigee. That said, the moon will be a little brighter than a normal full moon.

That full moon does, unfortunately, occur right at the time of the Geminid meteor shower. The peak nights of this famous shower are Dec. 12-13 and 13-14, from 12:01 a.m. to dawn each morning.

For all meteor showers, the viewing will be better after midnight. These repeating annual events are caused as the Earth enters debris left over from a specific comet (or, in the case of the Geminids, debris from an asteroid, 3200 Phaeton). As the Earth goes around the sun, our planet runs into the same debris at the same time each year. This is why these showers occur at the same time each year. After midnight, the part of the Earth that you are on is facing toward the debris that causes the meteor shower. This is why all meteor showers are better after midnight.

Meteor star showers are named for the constellation where the meteors appear to come from. By midnight in mid-December, the constellation of Gemini is high in the east. That said, don’t just look east; scan the entire sky for shooting stars. To view shooting star showers, find a dark location (as little city light as possible) and get comfortable (a lawn chair is a good idea). It’s still worth the effort this year, even if a semi-supermoon will make it challenging to see all but the brightest streaks of light.

December planets

Venus maintains the role it has had all fall as a blazing beacon in the western sky at dusk. In early December, Venus shines at minus 4.2 magnitude, is about a third of the way up in the western sky as it gets dark, and sets around 8:45 p.m. By the end of December, Venus is nearly halfway up in the west at dusk, shines at minus 4.2 and sets about 9:20 p.m.

For the first two weeks of December, Mercury behaves consistently for such a fast-moving planet. Look for Mercury at dusk about 6 degrees (the width of three fingers) above the western horizon. The elusive planet emerges around 6:15 p.m. and sets by 6:50 p.m. Spotting the planet will be easier in the first week of the month, since Mercury is a brilliant minus 0.4 magnitude for the first week of December. The planet remains brighter than zero magnitude through Dec. 14; after that, it will be harder to see it as the planet fades quickly midmonth. By Dec. 21, Mercury will have faded to 1.2 magnitude, and barely emerges from twilight before it sets.

Like Venus this month, Mars holds steady in December; Mars emerges halfway up in the southwest at dusk and sets just after 10 p.m. That said, Mars seems infinitely fainter than Venus. The red planet continues its slow fade from its springtime glory, dropping from 0.6 magnitude in early December to 0.9 at the end of the month.

Mercury, Venus and Mars can all be seen in the west at dusk in the early part of December; the tricky part is catching the lowest planet, Mercury, before it sets at 6:45 p.m. Venus can be your guide to the others, since it’s so bright. In early December, find Venus first, then look about 20 degrees above Venus for the pale amber spark of Mars, and 20 degrees below Venus for the bright dot of Mercury. By midmonth Venus appears closer to Mars than Mercury, but is still a great guide for locating the other two planets.

Look for the crescent moon to the lower right of Venus and just above Mercury, around 6:30 p.m. Dec. 1. On the following night, the moon will be beside Venus, and on Dec. 4, the moon stands to the lower right of Mars.

Jupiter, the sole dawn planet in December, comes up at 3 a.m. early in the month and is halfway up in the east at daybreak. By month’s end, the king of the planets rises at 1:20 a.m. and is two-thirds of the way up in the east at dawn. The planet shines at minus 1.8 magnitude — brighter than any star, but heading for much brighter times in the late winter, when it will shine at minus 2.4.

Saturn pops into the morning sky at the end of December. The ringed planet rises in the east at 5:45 a.m. Dec. 31, about 45 minutes before dawn washes it away.

Southern Cross returns

The Southern Cross, or Crux, missing as always from our skies from July through November, returns to our skies in early December. This compact constellation rises in the south-southwest right at daybreak on Dec. 1; by midmonth you will have an hour to find it from the time the cross rises at 5 a.m. to daybreak at 6:15 a.m. Prospects are much better by the last days of December; Crux rises in the south-southeast at 4 a.m. and is due south as day breaks at 6 a.m.

Mike Shanahan is director of Education, Exhibits and Planetarium. For more information, go to bishopmuseum.org/planetarium.html Opens in a new tab.