As we do every night, my daughter Katie and I walk Sunny, her big, beautiful, jowly Shar Pei. On our return home last night we both noticed how brilliant the moon looked. The way its light flooded our faces recalled the same joyful feeling you get when water sprays on your face while standing under the shower. You can never look directly at the sun, but it's perfectly safe to stare wide-eyed at the full moon and soak in all that good light. Tonight the moon will be full and even brighter.
Now that it's September, the full moon is noticeably higher in the sky compared to the low-slung June moon. Whatever the celestial sight, the higher it climbs, the brighter it appears. That's because we view it through less air compared to when it's closer to the horizon. Air not only absorbs light, but it also scatters away the blue and purple colors present in white light, tinting the moon, sun and even the stars shades of red and orange.
But why is tonight's full moon higher than June's? To understand why, recall that a full moon always lies directly opposite the sun. When the sun sets in the west, the moon rises 180 directly opposite in the eastern sky.
During the summer, the sun shines high in the sky near the summer solstice point in Taurus. Because the full moon sits 180 away it's near the winter solstice point in Sagittarius. That's the same place the sun will be on December 21st when it stands lowest in the southern sky. The June moon "gets there first" and like the winter sun, hovers low in the southern sky.
Come September, the sun is nearly 2½ months past the solstice and now shines lower in the sky than during early summer. Meanwhile, the full moon — still 180 opposite the sun — is now in the constellation Aquarius. Aquarius lies two constellations "up and over" from the winter solstice in Sagittarius, so of course the moon is both higher and brighter compared to June and July. Come December, when the sun sits lowest, the full moon blazes on high from the summer solstice point (see diagram above).
Tonight's full moon is traditionally known as the Full Corn Moon, but the Ojibwe people here in Minnesota know it better as the Full "Leaves Turning Moon." Not much corn grows in this nook of the planet, so I find the local name more relatable. The moment of maximum fullness occurs at 12:22 a.m. Central Time on Sept. 2, so if you stay up late, you can see the moon nearly 100 percent full. It's always just shy of 100 percent unless the lineup of sun-Earth-moon is precise which happens only during a lunar eclipse.
Tomorrow night the moon will be about 1 percent less full — will you be able to tell the difference? I never miss a full moonrise unless the weather's uncooperative, and I know a lot of you pin it to your list of monthly must-sees. To find out when the moon rises for your town, click here.
Essential equipment for moon-watching tonight and tomorrow include a location with a clear view to the east and a pair of binoculars, the better to see how the layers of air in our atmosphere distort the moon's outline and fringe it with color. Oh ... bring a camera, too!
Clear skies ...