Mercury and Saturn will share the same right ascension, with Mercury passing 38' to the south of Saturn.
From Cambridge however, the pair will not be observable – they will reach their highest point in the sky during daytime and will be no higher than 6° above the horizon at dawn.
Mercury will be at mag -0.3, and Saturn at mag 0.4, both in the constellation Sagittarius.
The pair will be a little too widely separated to fit comfortably within the field of view of a telescope, but will be visible to the naked eye or through a pair of binoculars.
A graph of the angular separation between Mercury and Saturn around the time of closest approach is available here.
The positions of the two objects at the moment of conjunction will be as follows:
| Object | Right Ascension | Declination | Constellation | Magnitude | Angular Size |
| Mercury | 18h11m00s | 23°10'S | Sagittarius | -0.3 | 5"5 |
| Saturn | 18h11m00s | 22°31'S | Sagittarius | 0.4 | 15"1 |
The coordinates above are given in J2000.0. The pair will be at an angular separation of 20° from the Sun, which is in Sagittarius at this time of year.
The sky on 13 Jan 2018
| The sky on 13 January 2018 | ||||||||||||||||||||||||||||||||||
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9% 26 days old |
All times shown in EST.
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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.
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| 06 Sep 2018 | – Saturn ends retrograde motion |
Image credit
The Moon in conjunction with Venus and Jupiter, with the Very Large Telescope in the foreground. Image © Y. Beletsky, ESO, 2009.