The almost-full waxing gibbous moon puts the constellation Cancer in the spotlight – but out of view – this Saturday night. Demure Cancer the Crab is the faintest constellation of the Zodiac. You can see it only on dark, moonless nights.
The starry sky is like a great big connect-the-dots book, enabling stargazers to star-hop from brighter stars to more obscure nighttime treasures. For instance, when the moon drops out of the evening sky by the month’s end, you can look for Cancer the Crab to show its delicate starlit figure in the region of sky in between the Leo star Regulus and the Gemini stars Castor and Pollux.
Our chart shows the eastern evening sky for North American mid-northern latitudes. But the night sky looks similar at northern latitudes from all around the world. The differences are not great. As seen from Europe and Asia, the moon shines closer to Gemini’s stars, Castor and Pollux, and farther away from Regulus, the brightest star in the constellation Leo the Lion. These little differences, as seen from around the world, are due to the moon’s own motion in orbit around Earth.
From the Southern Hemisphere, the differences are due in part to the moon’s movement, and in part to the difference in perspective from one hemisphere to the other. From the Southern Hemisphere tonight, Castor and Pollux appear to the left or upper left of the moon, whereas Regulus is found below the moon or to the moon’s lower right.
Still, we all live under the same sky, and no matter where you live worldwide, the moon beams in front of Cancer tonight, with Castor, Pollux, and Regulus nearby.
Just remember – although we outline Cancer for you on our chart, you’re not likely to see this constellation in tonight’s drenching moonlight. Notice the stars around it, and come back in a week or so to find the faint Crab when the moon has moved on its way – and left the evening sky dark for stargazing.