These next few evenings – December 23 and 24 – the nearly-full waning gibbous moon passes to the south of the Gemini stars, Castor and Pollux, and to the north of Procyon, the Little Dog star. The moon, as it goes full circle in front of the constellations of the zodiac, swings in between the Gemini stars and Procyon once every sidereal month.
Castor and Pollux might look meek in the moonlit glare these next couple of nights. Some of you may recall that Castor nearly coincides with the radiant point of the Gemini meteor shower, which peaked earlier this monrh.
There’s a tricky way to find the constellation Gemini, once the moon moves out of this part of the starry sky. Are you familiar with Orion the Hunter, the gem of all constellations? If so, you can star-hop from Orion to the constellation Gemini on a dark, moonless night. As depicted in the sky chart below, draw an imaginary line from Mintaka, the westernmost star of Orion’s Belt, through the bright ruddy star Betelgeuse.
At mid-northern latitudes, Orion and Gemnini rise at approximately the same time. At more southerly latitudes, like those in the Southern Hemisphere, Orion rises before Gemini. But no matter where you live worldwide – once the moon has moved to another part of the sky – Orion can serve as your ticket to locating the constellation Gemini the Twins.
Bottom line: The December 23, 2018 moon is in front of the constellation Gemini. Star-hop to Castor and Pollux – Gemini’s brightest stars – on this moonlit night. The star Castor is near the radiant point of the annual Geminid meteor shower.