Simulated image courtesy of Tom Ruen.

Moon at Last Quarter

Dominic Ford, Editor
From the Moon feed

Objects: The Moon
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The sky at

The Moon will pass last quarter phase, rising in the middle of the night and appearing prominent in the pre-dawn sky.

From Fairfield, it will be visible in the morning sky, becoming accessible around 01:27, when it reaches an altitude of 7° above your south-eastern horizon. It will then reach its highest point in the sky at 05:51, 34° above your southern horizon. It will be lost to dawn twilight around 06:42, 33° above your southern horizon.

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At this time in its monthly cycle of phases, it appears almost exactly half illuminated.

The Moon orbits the Earth once every four weeks, causing its phases to cycle through new moon, first quarter, full moon, last quarter, and back to new moon once every 29.5 days.

As it progresses through this cycle, it is visible at different times of day. At last quarter, it rises in the middle of the night and appears high in the sky by dawn. It sets at around lunchtime. More information about the Moon's phases is available here.

Observing the Moon at last quarter

Over coming days, the Moon will rise later each day, so that it is visible for less time before sunrise and rises less far above the eastern horizon before dawn. By the time it reaches new moon, it will rise at around dawn and set at around dusk, making it visible only during the daytime.

Its day-by-day progress is charted below, with all times are given in Fairfield local time.

Date Sun
rises at
rises at
Altitude of Moon
at sunrise
Direction of Moon
at sunrise
30 Jan 202107:0519:1715°west
31 Jan 202107:0520:2721°west
01 Feb 202107:0121:3927°west
02 Feb 202107:0222:5031°south-west
03 Feb 202107:0222:5532°south-west
04 Feb 202107:0200:0332°south-west
05 Feb 202106:5801:1730°south
06 Feb 202106:5802:3127°south
07 Feb 202106:5803:4322°south
08 Feb 202106:5404:4716°south-east
09 Feb 202106:5405:45south-east
10 Feb 202106:5406:32south-east

Seasonal variations

Although the Moon passes last quarter every month, it is more favourably placed in the pre-dawn sky at some times of year than others.

The last quarter moon appears high in the pre-dawn sky around the autumn equinox, but much lower towards the horizon around the spring equinox.

This is because it always lies close to a line across the sky called the ecliptic. This marks the flat plane in space in which all of the planets circle the Sun. It is the line through the zodiacal constellations that the Sun follows through the year.

The altitude at which the Moon appears above the horizon at sunrise depends how steeply the line of the ecliptic is inclined to the horizon. If the plane of the ecliptic meet the horizon at a very shallow angle, the Moon will rise or set along a line which is almost parallel to the horizon, and a large separation from the Sun along this line would still only correspond to a very low altitude in the sky.

The inclination of the ecliptic plane to the horizon at Fairfield varies between 72° (sunrise at the autumn equinox) and 25° (sunrise at the spring equinox). On February 4, the ecliptic is inclined at 29° to the eastern dawn horizon, as shown by the yellow line in the planetarium view above, meaning that on this occasion the Moon is poorly placed for viewing from Fairfield.

The Moon's position

At the moment it reaches last quarter, the Moon's distance from the Earth will be 370,000 km. Its celestial coordinates will be as follows:

Object Right Ascension Declination Constellation Angular Size
The Moon 14h56m40s -13°58' Libra 32'15"

The coordinates above are given in J2000.0.

The sky on 04 February 2021
Twilight ends
Twilight begins

22-day old moon
Waning Gibbous


22 days old

Rise Culm. Set
Mercury 07:13 12:39 18:04
Venus 06:29 11:17 16:06
Moon 00:03 05:35 10:59
Mars 10:32 17:39 00:45
Jupiter 06:50 11:47 16:44
Saturn 06:32 11:24 16:16
All times shown in EST.


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

04 Feb 2021  –  Moon at Last Quarter
10 Feb 2021  –  The Moon at perihelion
11 Feb 2021  –  New Moon
18 Feb 2021  –  The Moon at apogee

Image credit

Simulated image courtesy of Tom Ruen.






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