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

From Seattle, it will be visible in the dawn sky, rising at 02:39 (PST) – 3 hours and 31 minutes before the Sun – and reaching an altitude of 21° above the south-eastern horizon before fading from view as dawn breaks around 05:50.

Begin typing the name of a town near to you, and then select the town from the list of options which appear below.

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 daily progress is charted below, with all times are given in Seattle local time.

Date Sun
rises at
rises at
Altitude of Moon
at sunrise
Direction of Moon
at sunrise
14 Apr 201706:2022:2917°south-west
15 Apr 201706:1823:2720°south-west
16 Apr 201706:1600:2221°south
17 Apr 201706:1401:1323°south
18 Apr 201706:1202:0023°south
19 Apr 201706:1002:4222°south
20 Apr 201706:0803:2021°south-east
21 Apr 201706:0703:5518°south-east
22 Apr 201706:0504:2714°south-east
23 Apr 201706:0304:5710°east
24 Apr 201706:0105:27east
25 Apr 201705:5905:58east

The exact moment of last quarter

The exact moment of last quarter is defined as the time when the Moon's ecliptic longitude is exactly 90° away from the Sun's ecliptic longitude, as observed from the center of the Earth. However, the Moon does not appear in any way special at this instant in time, and a last quarter moon can be observed at any time in the pre-dawn sky.

At the moment it reaches last quarter, the Moon's distance from the Earth will be 396,000 km. Its celestial coordinates will be as follows:

Object Right Ascension Declination Constellation Angular Size
The Moon 20h03m20s 17°38'S Sagittarius 30'06"

The coordinates above are given in J2000.0.

The sky on 19 April 2017
Twilight ends
Twilight begins

22-day old moon
Waning Crescent


22 days old

Rise Culm. Set
Mercury 06:04 13:07 20:11
Venus 04:48 11:00 17:12
Moon 02:42 07:30 12:22
Mars 07:21 15:01 22:41
Jupiter 18:41 00:22 06:03
Saturn 00:48 05:06 09:25
All times shown in PDT.


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

19 Apr 2017  –  Moon at Last Quarter
26 Apr 2017  –  New Moon
02 May 2017  –  Moon at First Quarter
10 May 2017  –  Full Moon

Image credit

Simulated image courtesy of Tom Ruen.






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