Mercury and Neptune will share the same right ascension, with Mercury passing 1°20' to the south of Neptune.
From Cambridge however, the pair will not be observable – they will reach their highest point in the sky during daytime and will be 4° below the horizon at dawn.
Mercury will be at mag 0.5 in the constellation Cetus, and Neptune at mag 7.9 in the neighbouring constellation of Pisces.
The pair will be too widely separated to fit within the field of view of a telescope, but will be visible through a pair of binoculars.
A graph of the angular separation between Mercury and Neptune 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 | 00h52m20s | 2°38'N | Cetus | 0.5 | 8"3 |
| Neptune | 00h52m20s | 3°59'N | Pisces | 7.9 | 2"2 |
The coordinates above are given in J2000.0. The pair will be at an angular separation of 26° from the Sun, which is in Aries at this time of year.
The sky on 30 Apr 2031
| The sky on 30 April 2031 | ||||||||||||||||||||||||||||||||||
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63% 9 days old |
All times shown in EDT.
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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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Image credit
The Moon in conjunction with Venus and Jupiter, with the Very Large Telescope in the foreground. Image © Y. Beletsky, ESO, 2009.