Close approach of the Moon and Mars

Monday 23rd Dec 201903:53

The Moon and Mars will make a close approach, passing within 3°20' of each other. The Moon will be 27 days old.

From London, the pair will be difficult to observe as they will appear no higher than 17° above the horizon. They will be visible in the dawn sky, rising at 04:45 (BST) – 3 hours and 19 minutes before the Sun – and reach an altitude of 17° above the south-eastern horizon before fading from view as dawn breaks at around 07:36.

The Moon will be at mag -10.3, and Mars at mag 1.6, both in the constellation Libra.

The pair will be too widely separated to fit within the field of view of a telescope, but will be visible to the naked eye or through a pair of binoculars.

At around the same time, the two objects will also share the same right ascension – called a conjunction.

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 closest approach will be as follows:

Object Right Ascension Declination Constellation Magnitude Angular Size
The Moon 15h24m00s -14°42' Libra -10.3 31'52"3
Mars 15h19m30s -17°52' Libra 1.6 4"1

The coordinates above are given in J2000.0. The pair will be at an angular separation of 38° from the Sun, which is in Sagittarius at this time of year.

This entry in the observing calendar was provided by