We’ve hit a run of clear skies, so it feels like a shopping spree up there. Anything a skywatcher might want to see — sunsets, meteors, a last look at Saturn, the Milky Way, the latest comets — is easy pickings. It’s no wonder the hobby of astronomy can drive some people crazy with its boom and bust cycles in the everlasting battle with the clouds.
If you’ve got good weather, take advantage of the late sunrise to step outside and gawk at a great gathering of a splinter-thin crescent moon just 1° (two moon diameters) from the planet Mars tomorrow morning (Oct. 17). Only 6° below the pair, you’ll see the beacon of Venus like a spotlight directing your eyes to the action. Start looking about an hour-and-a-half before sunrise in the eastern sky or around 6 a.m. low in the eastern sky. All three rise higher in a brightening sky as the sun works its way to the horizon.
From mid-October through November is the best time to catch sight of another dawn phenomenon, the zodiacal light. It’s a big cone of diffuse light, broader at its base and tapering along its length, that tilts up from the eastern horizon shortly before the start of dawn. The soft, glowing nature of the light resembles the smoky look of the Milky Way. But while the Milky Way’s misty appearance comes from the combined light of billions of distant suns, the zodiacal light originates from the sunlight scattered off quadrillions (at least!) of tiny, dust-mote sized comet grains and bits of asteroid debris.
The dust nearest the sun gets lit up brightest, hence the bright and broad base of the cone. The farther you look up and away from the sun’s direction, the less intense the scattered light, the reason the cone tapers and fades. It’s an eerie thing to see and worth getting up a little earlier. The zodiacal light is easily visible from a dark, eastern sky starting about two hours before sunrise, but most impressive at the very start of twilight about 90 minutes before sunrise, when the eastern sky begins to brighten.
The crescent moon is thin and faint enough that the zodiacal light should return to view — at least faintly — tomorrow morning. After that through about Nov. 2nd, when the moon returns to the morning sky, it’s open season on comet dust watching!