Simulated image courtesy of Tom Ruen.

Moon at First Quarter

Dominic Ford, Editor
From the Moon feed

Objects: The Moon
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The sky at

The Moon will pass first quarter phase, appearing prominent in the evening sky and setting in the middle of the night.

From Ashburn , it will be visible from soon after it rises, at 12:58, until soon before it sets at 01:42.

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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 first quarter, it appears high in the sky at sunset before sinking towards the horizon and setting in the middle of the night. More information about the Moon's phases is available here.

Observing the Moon at first quarter

Over coming days, the Moon will set later each day, becoming visible for more of the night. Within a few days, it will not make it very far above the eastern horizon before nightfall. By the time it reaches full phase, it will be visible for much of the night, rising at around dusk and setting at around dawn.

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

Date Sun
sets at
sets at
Altitude of Moon
at sunset
Direction of Moon
at sunset
13 Jun 202120:3622:4922°west
14 Jun 202120:3623:3231°west
15 Jun 202120:3700:1039°west
16 Jun 202120:3700:4445°west
17 Jun 202120:3701:1350°south-west
18 Jun 202120:3801:4152°south-west
19 Jun 202120:3802:0850°south
20 Jun 202120:3802:3645°south
21 Jun 202120:3803:0737°south
22 Jun 202120:3903:4328°south-east
23 Jun 202120:3904:2618°south-east
24 Jun 202120:3905:18south-east

The exact moment of first quarter

The exact moment of first 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 first quarter moon can be observed at any time in the evening sky.

At the moment it reaches first quarter, the Moon's distance from the Earth will be 377,000 km. Its celestial coordinates will be as follows:

Object Right Ascension Declination Constellation Angular Size
The Moon 11h56m30s 5°53'N Virgo 31'40"

The coordinates above are given in J2000.0.

The sky on 17 Jun 2021

The sky on 17 June 2021
Twilight ends
Twilight begins

7-day old moon
Waxing Gibbous


7 days old

Rise Culm. Set
Mercury 05:23 12:29 19:36
Venus 07:17 14:44 22:10
Moon 12:29 19:10 01:41
Mars 08:34 15:49 23:03
Jupiter 00:18 05:43 11:07
Saturn 23:24 04:28 09:31
All times shown in EDT.


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

17 Jun 2021  –  Moon at First Quarter
24 Jun 2021  –  Full Moon
01 Jul 2021  –  Moon at Last Quarter
09 Jul 2021  –  New Moon

Image credit

Simulated image courtesy of Tom Ruen.





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