Mercury and Neptune will share the same right ascension, with Mercury passing 15' to the south of Neptune.
From South El Monte however, the pair will not be readily observable since they will be very close to the Sun, at a separation of only 20° from it.
Mercury will be at mag -0.4, and Neptune at mag 8.0, both in the constellation Ophiuchus.
The pair will be close enough to fit within the field of view of a telescope, but will also 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 | 17h13m00s | 21°52'S | Ophiuchus | -0.4 | 5"8 |
| Neptune | 17h13m00s | 21°37'S | Ophiuchus | 8.0 | 2"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 2 Sep 2025
| The sky on 2 September 2025 | ||||||||||||||||||||||||||||||||||
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75% 10 days old |
All times shown in PDT.
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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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| 27 Aug 1978 | – Neptune ends retrograde motion |
| 22 Mar 1979 | – Neptune enters retrograde motion |
| 10 Jun 1979 | – Neptune at opposition |
| 30 Aug 1979 | – Neptune 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.