The crescent moon, September 15, 2020

2020, October 18: Crescent Moon in West


Moon and Antares, October 18, 2020
2020, October 18: Thirty minutes after sunset, the moon (2.2 days after the New moon phase and 7% illuminated) is low in the southwest, nearly 15° to the right of Antares – the Heart of the Scorpion.

The crescent moon is low in the west about 30 minutes after sunset near the star Antares.  Four bright planets – Venus, Mars, Jupiter, and Saturn – are visible during the night.

by Jeffrey L. Hunt

Chicago, Illinois:  Sunrise, 7:07 a.m. CDT; Sunset, 6:04 p.m. CDT.  Check local sources for sunrise and sunset times in different locations.

Morning: Brilliant Venus and bright Mars continue to separate in the morning sky.  Venus rises in the east at about 4 a.m. CDT.  As morning twilight begins and grows brighter, the brilliant planet rises higher in the east and Mars, in the sky nearly all night, is low in the west.  What is the last date you see them together?  Mars sets as Venus rises (Venus – Mars opposition) on November 9.  Depending on the obstructions – trees, houses, or buildings – where you live and the clouds that are present near the horizon, you may be able to follow them until a few mornings before opposition. Both planets can be seen when near the horizon because of their brightness. Venus continues to step eastward in Leo.  See a detailed chart here.

Detailed morning note: Venus is 0.7° to the upper right of σ Leo.  One hour before sunrise, Venus is over 23° up in the east-southeast. At this time, Mars (m = −2.5) is 6.0° in altitude above the western horizon.  Forty-five minutes before sunrise, begin looking for Arcturus, low in the east-northeast.  Use a binocular.

See our summary about Venus during October 2020 and the feature article  about Venus as a Morning Star.

Evening:  Begin looking for the moon low in the south-southwest about 30 minutes after sunset.  Find a clear horizon.  The star Antares – the Heart of the Scorpion – is at about the same altitude as the lunar crescent, but about 15° to the left.  Your fist extended to arm’s length, covers about 10°, from the pinky finger to the thumb knuckle.  As the sky darkens further, you should be able to pick out the crescent moon and the star without optical help.  Moving farther south along the horizon, Jupiter and Saturn are less than one-third of the way up in the sky.  They are 6.2° apart.  Both planets are moving slowly eastward compared to the background stars in Sagittarius.  Jupiter is slowly overtaking the Ringed Wonder and catches it on December 21, 2020.  Bright Mars is in the eastern sky among the dim stars of Pisces.  It is retrograding, moving westward compared to the stars, in Pisces – an illusion as Earth passes the outer planets.  Use a binocular to make nightly observations of the planets compared to the starry background.

Detailed evening note: One hour after sunset, the moon (2.2 days after the New moon phase, 7% illuminated) is about 5° in altitude in the west-southwest and nearly 15° to the right of Antares (α Sco, m = 1.0).  Farther eastward, Jupiter is over 25° up in the south, with Saturn 6.2° to its upper left.  Both planets are moving eastward in Sagittarius.  In the starfield, Jupiter is 3.5° to the lower left of Pi Sagittarii (π Sgr) and 1.0° to the lower right of 50 Sagittarii (50 Sgr).  Saturn is 1.8° to the lower left of 56 Sagittarii (56 Sgr). Now it seems that a race is underway for Jupiter to catch up to and pass Saturn before the pair disappears into evening twilight.  Mars is 12° up in the east-southeast.  An hour later, the Red Planet is over 23° in altitude. This evening it is to the right of an imaginary line that connects Zeta Piscium (ζ Psc) and 89 Piscium (89 Psc).  The planet is 2.5° to the lower right of ζ Psc and 1.6° to the upper left of 89 Psc.  Additionally, Mars is 1.7° to the lower left of 80 Piscium (80 Psc, m =5.5) and 4.1° below Epsilon Piscium (ε Psc, m = 4.2).  Use a binocular to spot the planet in the dim starfield.

For more about the Great Conjunction, read our feature article. This is the closest Jupiter – Saturn conjunction since 1623.

Read more about the planets during October.

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