© 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.

1964 apparition of Saturn

14 Jun 1964 – Saturn enters retrograde motion
24 Aug 1964 – Saturn at opposition
01 Nov 1964 – Saturn ends retrograde motion

Observing Saturn

Saturn leaves retrograde motion as its 1964 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 22h06m10s 13°27'S Aquarius 0.5 17.7"

The coordinates above are given in J2000.0.

From Fairfield , it will be visible in the evening sky, becoming accessible around 17:21 (EDT), 29° above your south-eastern horizon, as dusk fades to darkness. It will then reach its highest point in the sky at 19:10, 35° above your southern horizon. It will continue to be observable until around 23:18, when it sinks below 10° above your south-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 July 2021
Sunrise
05:45
Sunset
20:17
Twilight ends
22:13
Twilight begins
03:49

17-day old moon
Waning Gibbous

82%

17 days old

Planets
Rise Culm. Set
Mercury 05:11 12:36 20:01
Venus 08:27 15:08 21:48
Moon 22:19 03:47 09:28
Mars 07:47 14:37 21:27
Jupiter 21:26 02:44 08:02
Saturn 20:30 01:25 06:21
All times shown in EDT.

Source

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

24 Aug 1964  –  Saturn at opposition
06 Sep 1965  –  Saturn at opposition
02 Apr 1966  –  Saturn ring plane crossing
15 Jun 1966  –  Equinox on Saturn

Image credit

© NASA/Cassini

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41.14°N
73.26°W
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