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 from soon after it rises, at 00:16, until soon before it sets at 11:31.

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 Fairfield local time.

Date Sun
rises at
Moon
rises at
Altitude of Moon
at sunrise
Direction of Moon
at sunrise
14 Jan 201707:1418:2514°west
15 Jan 201707:1419:3122°west
16 Jan 201707:1320:3628°west
17 Jan 201707:1321:3833°south-west
18 Jan 201707:1222:3836°south-west
19 Jan 201707:1223:3637°south-west
20 Jan 201707:1100:3437°south
21 Jan 201707:1101:3036°south
22 Jan 201707:1002:2633°south
23 Jan 201707:0903:2129°south
24 Jan 201707:0904:1423°south-east
25 Jan 201707:0805:0617°south-east

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 402,000 km. Its celestial coordinates will be as follows:

Object Right Ascension Declination Constellation Angular Size
The Moon 13h57m00s 7°21'S Virgo 29'41"

The coordinates above are given in J2000.0.

The sky on 19 Jan 2017

The sky on 19 January 2017
Sunrise
07:12
Sunset
16:53
Twilight ends
18:30
Twilight begins
05:35

21-day old moon
Waning Crescent

45%

21 days old

Planets
Rise Culm. Set
Mercury 05:39 10:19 15:00
Venus 09:20 15:05 20:50
Moon 23:36 05:31 11:19
Mars 09:39 15:31 21:23
Jupiter 23:45 05:22 10:58
Saturn 04:46 09:26 14:07
All times shown in EST.

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

19 Jan 2017  –  Moon at Last Quarter
27 Jan 2017  –  New Moon
03 Feb 2017  –  Moon at First Quarter
10 Feb 2017  –  Full Moon

Image credit

Simulated image courtesy of Tom Ruen.

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