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Young moon low in west after sunset

Tonight – August 23, 2017 – go young moon hunting. Look for the slender waxing crescent moon low in your western sky at dusk and nightfall. But don’t dilly-dally. The moon will follow the sun beneath the horizon by nightfall or early evening. Click here to find out the moon’s setting time in your sky, remembering to check the moonrise and moonset box.

The new moon occurred on August 21. Most of the time you can’t see the new moon. At new moon, the dark or nighttime side side of the moon faces Earth. Moreover, at the vicinity of new moon, the moon pretty much rises and sets with the sun, so it’s only out during the daylight hours and is lost in the sun’s glare.

But some of you might have actually seen the new moon silhouette during the solar eclipse on August 21, 2017. More often than not, however, the new moon avoids the Earth’s shadow by swinging above it or below it. From here on out, the new moon will swing above (north of) the Earth’s shadow for the next five months (September, October, November, December and January). Finally, on February 15, 2018, the north side of the moon will clip the southern part of the Earth’s shadow, to exhibit a partial solar eclipse over the far-southern part of the globe. Thereafter, the new moon will swing below (south of) the Earth’s shadow for months on end.

After any new moon, the moon travels eastward from the sun in Earth’s sky. A few days after new moon, the moon finally moves far enough east of the sun to appear as a very thin crescent in the west after sunset.

For the fun of it, let’s suppose we’re on the near side of the waxing crescent moon, looking back at our planet Earth. We’d actually see Earth displaying the opposite phase, whereby almost all of Earth is illuminated in sunshine, with only a tiny sliver of the Earth’s nighttime visible.

Image via EarthView. If you were on the near side of the moon as the sun sets over North America on August 23, 2017, you’d only see a tiny sliver of the Earth’s nighttime side (at far right). When the moon is a waxing crescent in Earth’s sky, then someone on the moon would see a waning gibbous Earth in the moon’s sky.

Thereby, the almost-full waning gibbous Earth reflects sunlight to the moon and then the dark side of the waxing crescent moon reflects the sunlight back to Earth. This twice-reflected sunshine is known as earthshine. Look for it to softly illuminate the dark side of the moon for the next few nights.

Binoculars may well enhance the view of earthshine. Binoculars also accentuate the three-dimensional view of the lunar terrain along the terminator – the shadow line crossing the lunar disk.

With the moon largely absent in the evening sky at present, these next several nights will also showcase The Teapot asterism in a dark country sky.

Bottom line: Look for the waxing crescent moon to grace your western sky after sunset for the next several days.

Bruce McClure