Mars and Neptune will share the same right ascension, with Mars passing 3°18' to the south of Neptune.
From South El Monte , the pair will become visible at around 19:33 (PST), 29° above your south-western horizon, as dusk fades to darkness. They will then sink towards the horizon, setting at 22:55.
Mars will be at mag 0.3, and Neptune at mag 8.0, both in the constellation Sagittarius.
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 Mars 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 |
| Mars | 17h55m40s | 25°35'S | Sagittarius | 0.3 | 7"8 |
| Neptune | 17h55m40s | 22°17'S | Sagittarius | 8.0 | 2"2 |
The coordinates above are given in J2000.0. The pair will be at an angular separation of 78° from the Sun, which is in Virgo at this time of year.
The sky on 16 Dec 2025
| The sky on 16 December 2025 | ||||||||||||||||||||||||||||||||||
|
7% 26 days old |
All times shown in PST.
|
|||||||||||||||||||||||||||||||||
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
| 09 Sep 1984 | – Neptune ends retrograde motion |
| 04 Apr 1985 | – Neptune enters retrograde motion |
| 23 Jun 1985 | – Neptune at opposition |
| 12 Sep 1985 | – 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.