Watch for a daytime morning moon

At top: Stefanie Bush caught a daytime moon in 2018 with an iPhone X, in the midst of anticrepuscular rays, over Lake Hollingsworth in Lakeland, Florida.

This week’s full supermoon came on the night of April 26-27, 2021, and by April 28 the moon is in a waning gibbous phase, rising later and later on successive nights. For the mainland United States, the April 28 moon rises in the southeast, roughly two to three hours after sunset. A later rising time, of course, means a later setting time. That’s why the coming mornings are a good time to catch a nearly full daytime moon over your western horizon after sunrise. Watch for it!

The moon is up in the daytime half of the time. But, because it’s pale against the blue sky, it’s not as noticeable during the day as at night. However, there are certain times of the month when the daytime moon is noticeable. Late April/early May 2021 presents one of those windows for catching a daytime moon.

Around the evening of April 28, the moon, and the nearby bright star Antares, rise at mid-to-late evening at mid-northern latitudes. See the chart below. From the Southern Hemisphere, the moon and Antares rise at early-to-mid evening. Because of Earth’s motion around the sun, Antares – like all the fixed stars – will rise about four minutes earlier each evening. Meanwhile, because of its own motion around Earth, the moon will be rising later and later each evening and thus moving away from Antares’ location in the sky.

Day by day, in the days ahead, the lighted portion of the waning gibbous moon will shrink. The half-lit last quarter moon will come on May 3, 2021.

Chart: 3 positions of moon and the bright star Antares with slanted green line of ecliptic.

No matter where you are on Earth, the moon is in the eastern half of the sky on the evenings of April 27, 28 and 29 (look later and later each evening after full moon on April 27, 2021). The bright star nearby is Antares, Heart of the Scorpion, in the constellation Scorpius. Then – especially by April 29, when the moon is noticeably waning – look westward after sunrise for the daytime moon.

Diagram: 4 positions of moon in the southwest daytime sky with slanted ecliptic line.

The moon in the daytime sky after sunrise in late April and early May 2021, at mid-northern North American latitudes. In the Southern Hemisphere, the tilt of the ecliptic (the blue line on the chart) is much steeper than at northerly latitudes. From more southerly latitudes, the daytime moon will climb more upward than sideways with each passing day.

Huge very faint pale moon against blue sky behind radio tower with large round antennas.

You’ll often miss the moon during the day because it’s so pale against the blue daytime sky. Look closely these next few mornings, especially in the hours after sunrise. Look west! You’ll see it. Our friend Jenney Disimon in Sabah, North Borneo, caught this daytime moon on January 4, 2018.

Why is the daytime moon most noticeable now? The moon is up during the day half the time. It must be, since it orbits around the whole Earth once a month. A crescent moon is hard to see, though, because it’s so near the sun in the sky. At the vicinity of last quarter moon about a week from now, you might have to crane your neck, looking up, to notice it after sunrise.

The moon in late April/early May is noticeable simply because the moon is still showing us most of its lighted face; it appears large in our sky. Also, in the hours after sunrise, the moon is fairly near the western horizon, so people out and about might catch sight of it.

At mid-northern latitudes in North America, the moon will set about two hours after sunrise on April 29. It’ll set roughly one hour later after sunrise each day thereafter.

These recommended almanacs can help you find the moon’s setting time in your sky

Pale gibbous moon against sky-blue background.

Daytime moon seen on December 18, 2010. Image by Brian Pate. Used with permission.

Bottom line: The moon is now in a waning gibbous phase. Beginning around April 29 – shortly after sunrise – you’ll see it floating pale and beautiful against a blue sky. Look west!

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Bruce McClure