Tonight – January 29, 2018 – the moon might look full to you, but it’s not yet. Full moon comes when the moon is most opposite the sun. That’ll be during the morning hours on January 31 for us in North America, and, of course, this full moon is a Blue Moon, and a supermoon and will undergo a total eclipse – a super Blue Moon eclipse. Meanwhile, the January 29 moon is a waxing gibbous moon. It’s near the bright stars Castor and Pollux in the constellation Gemini the Twins.
Although we’ve drawn in the stick figure of the Gemini Twins on the chart at the top of this post, you might not see much of Gemini in the moonlight glare except for Castor and Pollux. These two stars are bright and noticeable for being near one another. They form the northeastern part of the Winter Circle.
That brilliant star on the other side of the January 29 moon is Procyon, sometimes called the Little Dog Star.
You might not know that Procyon – and Castor and Pollux – offer an alternate way of finding Polaris, the North Star. You can draw an imaginary line from Procyon and then in between the two Gemini stars, and then take a long jump northward to locate Polaris, the North Star.
Bottom line: On the night of January 29, 2018, let the full-looking waxing gibbous moon guide your eye to the bright Gemini stars, Castor and Pollux!
Bruce McClure has served as lead writer for EarthSky's popular Tonight pages since 2004. He's a sundial aficionado, whose love for the heavens has taken him to Lake Titicaca in Bolivia and sailing in the North Atlantic, where he earned his celestial navigation certificate through the School of Ocean Sailing and Navigation. He also writes and hosts public astronomy programs and planetarium programs in and around his home in upstate New York.