On September 17, 2020, the new moon crossed 5° north of the sun, heading out of the morning sky and into the night sky. The day the new moon occurs, we cannot see it at all. This happens because it rises and falls with the sun (more or less) and is lost in the sun’s light during the day. However the moon still returns; on September 18, 19, 20, and 21, you will see the moon as a crescent in the west. This can happen in one or more of these nights, after sunset.
In the days following the new moon, as the moon proceeds its steady path across the earth, it is easy to spot the moon rising east of the sun on the dome of the sky. That’s a little further from the sunset each night. Fortunately for us, the moon will hit its perigee – the nearest position to Earth in its monthly orbit – on September 18, 2020.
This means that the new moon is moving away from the sun at a high orbital speed at the moment. Therefore, we’re predicting that a number of attentive viewers may see the young whisker-thin, crescent moon on the evening of the 18th of September.
To increase your possibility of seeing the young moon on September 18, search for a clear horizon in the sun’s direction. If you’ve got that, carry your binoculars along. Look west, near the sunset point on the horizon, for a pale crescent about 45 minutes to one hour after sunset.
However, you should not move slowly!
From many locations around the planet, the new moon of September 18th follows the sun below the horizon before nighttime. Therefore, it will not come back to the night sky until after sunset on the next day (September 19).
The moon will be more than one day (24 hours) old at sunset for nearly the whole world on September 18, 2020. And so, it would take a deliberate effort to spot the slender crescent. If you don’t catch the moon after sunset on the 18th of September, use your chance for the next few days. Every day, at dusk, a larger and lighter lunar crescent rises higher in the atmosphere and remains out longer after sunset.
Australia – the best location to catch a young moon!
Usually, it’s hard to catch a moon that is less than one day old (less than 24 hours after the new moon). But if there’s any location that may capture a moon less than 24 hours after the new moon, it’s Australia. Young moons in September are better to see from the Southern Hemisphere than the Northern Hemisphere. This is the reason why a moon remains out longer after sundown in late winter or early spring than in later summer or early autumn.
This young moon occurs only a few days before the spring equinox of the Southern Hemisphere and the fall equinox of the Northern Hemisphere. At sunset on the spring equinox, the ecliptic –regular course of the sun and estimated monthly path of the moon – reaches the horizon at the steepest angle for the year.
On the contrary, at dusk on the autumn equinox, the ecliptic reaches the horizon at its shallowest angle for the year. Consequently, everything else being equal, the Southern Hemisphere has the advantage to capture every young moon of September.
But, this time around, this moon is a little north of the ecliptic.
On a degree, the more northerly moon partly takes away the advantage of the Southern Hemisphere and the downside of the Northern Hemisphere. Then again, the Southern Hemisphere has the overall benefit of seeing the moon in September! The planet Mercury and the bright star Spica are in the proximity of the moon. However, these powerful stars will be hidden in the afterglow of the sunset at the northern latitudes. Because Mercury and Spica are located south of the ecliptic, they are much easier to see from the Southern Hemisphere. We compare Philadelphia, Pennsylvania (40 degrees north Latitude), USA, with Valdivia, Chile (40 degrees south latitude), both of which remain close to the same meridian: 75 degrees west longitude.
Moon sets one hour 10 minutes after the sun on September 18
Mercury sets 48 minutes after the sun on September 18
Spica sets 56 minutes after the sun on September 18
Moon sets one hour and 38 minutes after the sun on September 18
Mercury sets one hour and 56 minutes after the sun on September 18 Spica sets 2 two hours and 21 minutes after the sun on September 18