© NASA/Cassini

Saturn ends retrograde motion

Dominic Ford, Editor
From the Outer Planets feed

Objects: Saturn
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Saturn will reach the end of its retrograde motion, ending its westward movement through the constellations and returning to more usual eastward motion instead. This reversal of direction is a phenomenon that all the solar system's outer planets periodically undergo, a few months after they pass opposition.

The retrograde motion is caused by the Earth's own motion around the Sun. As the Earth circles the Sun, our perspective changes, and this causes the apparent positions of objects to move from side-to-side in the sky with a one-year period. This nodding motion is super-imposed on the planet's long-term eastward motion through the constellations.

The diagram below illustrates this. The grey dashed arrow shows the Earth's sight-line to the planet, and the diagram on the right shows the planet's apparently movement across the sky as seen from the Earth:

The retrograde motion of a planet in the outer solar system. Not drawn to scale.

2149–2150 apparition of Saturn

09 Oct 2149 – Saturn enters retrograde motion
15 Dec 2149 – Saturn at opposition
20 Feb 2150 – Saturn ends retrograde motion

Observing Saturn

Saturn leaves retrograde motion as its 2149–2150 apparition comes to an end, although it will remain visible for some weeks in the dusk sky.

Its celestial coordinates as it leaves retrograde motion will be:

Object Right Ascension Declination Constellation Magnitude Angular Size
Saturn 05h11m10s 21°42'N Taurus -0.3 19.2"

The coordinates above are given in J2000.0.

From Fairfield , it will be visible in the evening sky, becoming accessible around 17:58 (EST), 66° above your south-eastern horizon, as dusk fades to darkness. It will then reach its highest point in the sky at 19:00, 70° above your southern horizon. It will continue to be observable until around 01:26, when it sinks below 9° above your western horizon.

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Over the following weeks, Saturn will reach its highest point in the sky four minutes earlier each night, gradually disappearing into evening twilight.

The sky on 27 January 2022
Twilight ends
Twilight begins

25-day old moon
Waning Crescent


25 days old

Rise Culm. Set
Mercury 06:21 11:22 16:23
Venus 05:05 10:10 15:14
Moon 02:30 07:27 12:16
Mars 05:01 09:34 14:07
Jupiter 08:30 13:57 19:23
Saturn 07:34 12:34 17:35
All times shown in EST.


The circumstances of this event were computed using the DE430 planetary ephemeris published by the Jet Propulsion Laboratory (JPL).

This event was automatically generated by searching the ephemeris for planetary alignments which are of interest to amateur astronomers, and the text above was generated based on an estimate of your location.

Related news

15 Dec 2149  –  Saturn at opposition
30 Dec 2150  –  Saturn at opposition
13 Jan 2152  –  Saturn at opposition
26 Jan 2153  –  Saturn at opposition

Image credit

© NASA/Cassini






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