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2021, August 25: Retrograding Saturn and Jupiter

Saturn through the Hubble Space Telescope

A Hubble View of Saturn (NASA)


August 25, 2021: Evening Star Venus, bright Jupiter, and Saturn are visible during the early evening hours.  Brilliant Venus is in the western sky.  Jupiter and Saturn are in the southeastern sky.

Chart Caption – 2021, August 25: During the early evening hours, Jupiter and Saturn are in the southeastern sky in front of the stars of Capricorni.

by Jeffrey L. Hunt

Chicago, Illinois:  Sunrise, 6:10 a.m. CDT; Sunset, 7:35 p.m. CDT.  Check local sources for sunrise and sunset times for your location.

Three bright planets shine during the evening hours.  Venus is in the western sky among the stars of Virgo.

Bright Jupiter and Saturn are in the eastern sky.  They are retrograding in Capricornus.

Retrograde motion is an illusion as our faster moving planet passes Jupiter and Saturn.  We passed Saturn on August 2 and Jupiter less than a week ago.

Normally the planets appear to move eastward compared to the distant stars. They rise and set each day while Earth rotates.  On a larger scale, the result of the combined motions of the planets and Earth around the sun is that their normal progress in the sky is eastward compared to the stars. 

As Earth overtakes the planets, they seem to stop moving eastward and seem to go backwards compared to the starry background.  This is the illusion of retrograde.  Saturn retrogrades until nearly mid-September and Jupiter’s reverse motion ends a week later.

The stars of Capricornus are not very bright.  A binocular is helpful to find them.

Jupiter is the bright “star” in the southeastern sky during the early evening hours.  Saturn is bright, but dimmer than Jupiter.  The Ringed Wonder is 18.0° to the upper right of the Jovian Giant.

Jupiter is 2.7° to the upper right of Iota Aquarii (ι Aqr on the chart), 0.5° to the lower left of Mu Capricorni (μ Cap) and 2.9° to the upper left of Deneb Algedi – “the kid’s tail.”

Saturn is 1.1° to the lower left of Upsilon Capricorni (υ Cap).

Detailed Daily Note: One hour before sunrise, the moon (16.8d, 91%) is over 39° above the southwest horizon.  Farther westward along the ecliptic, Jupiter is about 6° above the west-southwest horizon.  Twenty-five minutes after sunset, Mercury is over 4° up in the west, 17.7° to the lower right of Venus.  Use a binocular to see them. Forty-five minutes after sunset, Venus is about 8° above the west-southwest horizon, 2.8° to the lower left of Porrima and 12.7° to the lower right of Spica, that is nearly 11° above the west-southwest horizon. Through a telescope, Venus is an evening gibbous phase, 14.5” across and 75% illuminated.  Farther eastward, Saturn is nearly 17° up in the southeast.  Jupiter, 18.0° of ecliptic longitude east of Saturn, is 10.0° up in the east-southeast.  Jupiter is 134.9° of ecliptic longitude east of Venus.  The combination of Venus’ rapid eastward motion and Jupiter’s slow retrograde reduced the gap between them by 6.5° in five evenings.  Venus, Saturn, and Jupiter are easier to see at the same time.  Three hours after sunset, the moon (17.6d, 86%) is about 11° up in the east.  Farther westward, Jupiter is over 28° up in the southeast, 2.7° to the upper right of ι Aqr, 0.5° to the lower left of μ Cap, and 2.9° to the upper left of Deneb Algedi.  Saturn, slightly higher than Jupiter, is above the south-southeast horizon, 1.1° to the lower left of υ Cap.  Both giant planets continue to retrograde in Capricornus.


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