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 Seattle , it will become visible around 21:34 (PDT), 31° above your south-western horizon, as dusk fades to darkness. It will then sink towards the horizon, setting 3 hours and 56 minutes after the Sun at 01:06.

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 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 Seattle local time.

Date Sun
sets at
Moon
sets at
Altitude of Moon
at sunset
Direction of Moon
at sunset
04 Jul 201921:1323:0116°west
05 Jul 201921:1323:3823°west
06 Jul 201921:0900:1029°west
07 Jul 201921:1000:3632°south-west
08 Jul 201921:1001:0234°south-west
09 Jul 201921:1001:2633°south-west
10 Jul 201921:1001:5331°south
11 Jul 201921:0602:2327°south
12 Jul 201921:0602:5622°south
13 Jul 201921:0703:3417°south-east
14 Jul 201921:0704:1611°south-east
15 Jul 201921:0705:10south-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 372,000 km. Its celestial coordinates will be as follows:

Object Right Ascension Declination Constellation Angular Size
The Moon 13h09m40s 1°40'S Virgo 32'01"

The coordinates above are given in J2000.0.

The sky on 09 July 2019
Sunrise
05:22
Sunset
21:10
Twilight ends
--:--
Twilight begins
02:30

7-day old moon
Waxing Gibbous

55%

7 days old

Planets
Rise Culm. Set
Mercury 07:05 14:23 21:41
Venus 04:36 12:33 20:31
Moon 13:49 19:44 01:26
Mars 06:50 14:29 22:08
Jupiter 18:42 23:00 03:18
Saturn 20:58 01:17 05:35
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

09 Jul 2019  –  Moon at First Quarter
16 Jul 2019  –  Full Moon
24 Jul 2019  –  Moon at Last Quarter
31 Jul 2019  –  New Moon

Image credit

Simulated image courtesy of Tom Ruen.

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122.33°W
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