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 02:23 (PDT) – 2 hours and 56 minutes before the Sun – and reaching an altitude of 20° above the south-eastern horizon before fading from view as dawn breaks around 04:55.

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

Date Sun
rises at
Moon
rises at
Altitude of Moon
at sunrise
Direction of Moon
at sunrise
21 May 201905:2222:5215°south-west
22 May 201905:2223:5018°south
23 May 201905:2200:3820°south
24 May 201905:2201:1822°south
25 May 201905:1801:5222°south
26 May 201905:1902:1822°south-east
27 May 201905:1902:4221°south-east
28 May 201905:1903:0520°south-east
29 May 201905:1503:2817°east
30 May 201905:1503:4814°east
31 May 201905:1504:1110°east
01 Jun 201905:1504:37east

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 404,000 km. Its celestial coordinates will be as follows:

Object Right Ascension Declination Constellation Angular Size
The Moon 22h32m30s 13°13'S Aquarius 29'33"

The coordinates above are given in J2000.0.

The sky on 26 May 2019
Sunrise
05:19
Sunset
20:55
Twilight ends
23:35
Twilight begins
02:39

22-day old moon
Waning Crescent

45%

22 days old

Planets
Rise Culm. Set
Mercury 05:35 13:31 21:28
Venus 04:33 11:43 18:52
Moon 02:18 07:25 12:37
Mars 07:21 15:24 23:28
Jupiter 22:01 02:17 06:33
Saturn 23:59 04:20 08:41
All times shown in PDT.

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

26 May 2019  –  Moon at Last Quarter
03 Jun 2019  –  New Moon
09 Jun 2019  –  Moon at First Quarter
17 Jun 2019  –  Full Moon

Image credit

Simulated image courtesy of Tom Ruen.

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47.61°N
122.33°W
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