Last quarter moon on April 4, 2021

Above photo: April Singer caught the last quarter moon of March 16, 2020.

This month’s last quarter moon comes on April 4, 2021, at 10:02 UTC. For U.S. time zones, that translates to 6:02 a.m. EDT, 5:02 a.m. CDT, 4:02 a.m. MDT and 3:02 a.m. PDT. Get up around sunrise April 4 to see the moon at or near its half-illuminated last quarter phase. The lit half points eastward (in the direction of sunrise), while the dark half points westward (in the direction of sunset).

From around the world, the moon will climb highest up for the day (to reach its “noontime” position) at or around sunrise April 4. From the Northern Hemisphere, the moon will lurk low in the southern sky, simulating the position of winter noonday sun; and from the Southern Hemisphere, the moon will be way up high, assuming the position of the summer noonday sun.

Find out which constellation of the zodiac backdrops the moon at Heavens-Above.

It’s sometimes said that the last quarter moon rises around midnight and sets around noon. By midnight, we mean midway between sunset and sunrise; and by noon, midway between sunrise and sunset. However, this rule of thumb falters somewhat when we talk about near-equinox last quarter moons. This upcoming last quarter moon will be the first last quarter moon to take place after the March 20 equinox, the Northern Hemisphere’s spring equinox and the Southern Hemisphere’s autumn equinox.

Want to find out when the moon rises and reaches its last quarter phase in your part of the world? Visit Sunrise Sunset Calendars, remembering to check the moon phases and moonrise and moonset boxes.

Diagram with Earth in center and moon phases around it in a circle.
A quarter moon happens whenever the sun-Earth-moon angle makes a right angle in space, with our planet Earth being at the vertex of this right angle. Image via Wikipedia.

By definition, the moon is at western quadrature – 90 degrees west of the sun in ecliptic longitude – at last quarter moon. Therefore, the last quarter moon assumes the sun’s position on the zodiac for 1/4 year (three months) previously, or where the sun was residing on or near January 4. In early January, the short winter days provide considerably less than 12 hours of sunlight at northerly latitudes, and, at southerly latitudes, the long summer days feature considerably more than 12 hours of sunlight.

The same holds true for the any last quarter moon happening near the March equinox. This upcoming last quarter moon will stay above the horizon for less than 12 hours at northerly latitudes, rising after midnight and setting before noon. Yet, in the Southern Hemisphere, the moon will rise before midnight and set in the afternoon.

Many people are aware that the sun reaches its northernmost point for the year at the June solstice and southernmost point at the December solstice. The moon does likewise, except that the moon swings to its northernmost point and southernmost point on a monthly basis, instead of just yearly. Sometimes, the moon’s northernmost or southernmost point for the month is called a lunar standstill, rather than a solstice.

This month – April 2021 – the moon reaches its southern lunar standstill (25.4 degrees south) on April 4 at 02:08 UTC, and its last quarter phase on April 4, at 10:02 UTC. April 4 presents the year’s closest coincidence of last quarter moon and southern lunar standstill.

Bottom line: Celebrate the year’s southernmost last quarter moon by getting up early on April 4, 2021, and looking for the half-lit moon.

April 3, 2021

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Bruce McClure

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