The Moon and Mars will share the same right ascension, with the Moon passing 5°52' to the north of Mars. The Moon will be 5 days old.
At around the same time, the two objects will also make a close approach, technically called an appulse.
From Fairfield , the pair will become visible at around 18:36 (EST), 21° above your southern horizon, as dusk fades to darkness. They will then sink towards the horizon, setting 3 hours and 50 minutes after the Sun at 21:53.
The Moon will be at mag -11.5, and Mars at mag 0.5, both in the constellation Sagittarius.
The pair will be too widely separated to fit within the field of view of a telescope or pair of binoculars, but will be visible to the naked eye.
A graph of the angular separation between the Moon and Mars 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 |
| The Moon | 18h33m20s | 19°13'S | Sagittarius | -11.5 | 32'15"2 |
| Mars | 18h33m20s | 25°05'S | Sagittarius | 0.5 | 6"8 |
The coordinates above are given in J2000.0. The pair will be at an angular separation of 70° from the Sun, which is in Virgo at this time of year.
The sky on 21 Oct 2031
| The sky on 21 October 2031 | ||||||||||||||||||||||||||||||||||
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38% 5 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.