Starwatch: full moon to pass through three constellations

This week, the full moon will cruise through three zodiacal constellations. First Gemini, the twins; then Cancer, the crab; and finally Leo, the lion.

The chart shows the view at 2100 GMT on 17 January, looking east-south-east from London. The moon will be full and sitting just below the two brightest stars of Gemini: Castor and Pollux. The brighter of the two, and the star nearest to the moon, is the yellow-tinged Pollux, while the one above is the whiter but dimmer Castor.

A day later, the moon will be smack in the middle of Cancer. Although with 99% of the moon’s visible surface still illuminated, it could be difficult to see the faint stars of the constellation. But the moon does make a straight line with two other bright stars. These are Procyon in Canis Minor, the lesser dog, and Sirius in Canis Major, the great dog.

By Wednesday, the moon will be in Leo, poised between the orange-tinged glow of Algieba, and the brighter white light of Regulus. The view can also be seen from the southern hemisphere. From Sydney in Australia, it is best seen later in the evening, around midnight.