2021, October 10:  Saturn’s Retrograde Ends

October 10, 2021:  Saturn’s retrograde ends this evening.  It slowly resumes its eastward motion compared to the starry background.  The bright planet pack – Venus, Jupiter, and Saturn – is easily visible after sunset.

2021, October 10: Saturn’s retrograde ends in western Capricornus.
Chart Caption – 2021, October 10: Saturn’s retrograde ends in western Capricornus.

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by Jeffrey L. Hunt

Chicago, Illinois:  Sunrise, 6:58 a.m. CDT; Sunset, 6:17 p.m. CDT.  Check local sources for sunrise and sunset times for your location.

Daily notes for October 2021

VENUS AS AN EVENING STAR 2021

Saturn’s retrograde ends this evening in western Capricornus.  The planet has been slowly moving westward compared to the stars since May 22.

The illusion of retrograde is from our faster moving planet overtaking and moving between the sun and the planet, known as opposition.  For several days before and after opposition – that occurred on August 2 for Saturn – the planet seems to stop moving eastward compared to the stars and reverses its direction.

The motion of the planets compared to the stars is a combination of the planets’ orbits around the sun.  The farther away from the sun, the slower the planet moves.  Saturn is nearly 10 times farther away from the sun as Earth.  That is nearly double Jupiter’s distance.

Saturn seems to be dawdling eastward. As Earth catches up, compared to the distant stars, the Ringed Wonder stops its eastward plod and seems to move backwards.

Saturn appears in front of Capricornus, to the lower right of Upsilon Capricorni (υ Cap on the chart).  Because the planet is on a very slow track compared to the other bright planets, it seems slow to get started eastward.  By month’s end, it moves less than 0.4° eastward.  In comparison, Venus moves over 1° eastward each evening.

Use a binocular to watch Saturn gently move eastward during the next several evenings.

Jupiter’s retrograde ends on October 18.  The Jovian Giant is in eastern Capricornus, near the stars Deneb Algedi and Nashira.

After Jupiter’s retrograde ends, the gap between the planets continues to close slightly as Saturn moves eastward and Jupiter seems to begin to pick up eastward speed.  The closest gap is 15.36° on October 24. Jupiter moves faster eastward and moves farther away from Saturn.  They are close together again at their Great Conjunction in 2040.

The chart above shows the constellation with the planets.  The starfields near Jupiter and Saturn are identified at two hours after sunset, when the planets are high in the southern sky.

2021, October 10: The crescent is moon is to the upper left of Antares, while Venus is to the lower left of Dschubba.
Chart Caption – 2021, October 10: The crescent is moon is to the upper left of Antares, while Venus is to the lower left of Dschubba.

Earlier during the evening, Evening Star Venus, Jupiter and Saturn are visible at the same time.  The Jovian planets are in the southeastern sky, while Venus is in the southwest.

Just one evening after a grouping of Venus, the crescent moon, and the three stars of the Scorpion’s head, the moon has moved eastward and its phase has grown slightly. The thick lunar slice is 9.5° to the upper right of Antares.

Forty-five minutes after sunset, Venus is nearly 10° up in the southwest.  It is 1.2° to the lower left of Dschubba and 6.4° to the lower right of Antares.

Unlike pokey Saturn, evening observations reveal its movement away from Dschubba and toward Antares.

Detailed Daily Note: Forty-five minutes after sunset, the crescent moon (4.5d, 26%) is nearly 16° up in the south-southwest, 9.5° to the upper left of Antares.  Brilliant Venus, nearly 10° up in the southwest, is 1.2° to the lower left of Dschubba and 6.4° to the lower right of Antares. Through a telescope, Venus is an evening gibbous, 58% illuminated and 20.6” across.  Farther eastward, Jupiter (m = −2.6), nearly 26° above the southeast horizon, is 15.5° to the left of Saturn.  The Ringed Wonder is nearly 27° above the south-southeast horizon.  Saturn haults its apparent westward motion and begins its direct motion today.  The gap between Jupiter and Saturn continues to close until October 24, at a minimum separation of 15.3°. Jupiter’s retrograde continues until October 18, but as Jupiter is reversing course and beginning to pick up eastward speed, Saturn’s eastward motion closes the gap to that minimum separation. By month’s end, the separation between them grows at about 0.01° each night.  Two hours after sunset, Jupiter is nearly 32° up in the south-southeast.  In the starfield, the Jovian Giant is 3.7° to the lower right of dim μ Cap, 2.0° to the upper right of Deneb Algedi, and 1.4° above Nashira. Slightly west of the meridian, Saturn is nearly 29° up in the sky, 1.5° to the lower right of υ Cap.

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