Tonight – October 21, 2016 – and for the next few nights, if you look outside fairly late at night, you’ll find the moon. It’s a waning gibbous moon on October 21. On October 22, the moon will be at the last quarter phase. This waning moon is ascending over your eastern horizon late at night. For the next several nights, it’s traveling across our sky in the company of the constellation Gemini the Twins, to the south of the bright Gemini stars, Castor and Pollux.
At mid-northern latitudes on October 21, the moon and Gemini stars won’t rise above the horizon till around 10 p.m. local time (11 p.m. local Daylight Saving Time). Farther south, the moon and Gemini stars rise even later.
If you’re not a night owl, you’re better off to wake up early and see the moon with the Gemini stars before dawn. Want to know when the star Castor rises into your sky? Click here.
On the other hand, if you are a night owl, look eastward and you might catch the moon, Castor and Pollux over your horizon before bedtime. At mid-northern latitudes, the constellation Orion and the Gemini stars, Castor and Pollux, rise over the eastern horizon at roughly the same time. So if you are familiar with Orion the Hunter, and up at late evening, look to the north (or left) of Orion to see Castor and Pollux.
At more southerly latitudes, Orion rises before the Gemini stars do. But in either the Northern Hemisphere or Southern Hemisphere, an imaginary line drawn from the brilliant star Rigel through the brilliant star Betelgeuse faithfully escorts you to Castor and Pollux. If you live in the Southern Hemisphere, remember that Castor and Pollux will appear below the moon and the star Procyon above the moon.
Familiar with the Big Dipper? If so, the Big Dipper can also escort you to the Gemini stars. Draw an imaginary line diagonally through the bowl of the Big Dipper, from the star Megrez through the star Merak. You are going in the direction opposite of the Big Dipper handle. This line will point to Castor and Pollux. Of course, the Big Dipper is more easily seen from the Northern Hemisphere.
Bottom line: Let the moon guide you to the brightest stars in the constellation Gemini, Castor and Pollux, on the nights of October 21, 22 and 23, 2016.