Full Red Moon Of August Is Blue Too

The nearly full moon grazes the treetops during twilight last night July 31. Tonight it will be fully illuminated by the sun and shine brightly in the constellation Capricornus. Photo: Bob King

With 31 days in August and a full moon happening tonight, we’re guaranteed a second full moon at the end of the month. A fine pair of bookends these. Full moons are often known by multiple names; the two most common for August are the Sturgeon Moon and Red Moon. We’ll need them both this month.

The first refers to the good sturgeon fishing this time of year for Indians living in the Great Lakes region. “Red” comes from the color the moon often appears during the summer months, when haze, humidity and low altitude conspire to change its tint from white to ruddy. The second full moon in a month is also called a Blue Moon. Blue Moons happen about once every two or three years – this one occurs on the 31st. That means this month’s Red Moon will also be Blue!

July’s full moon in Sagittarius was about as low as a full moon gets. Tonight the moon will be in Capricornus and noticeably higher up (almost three fists) compared to last month. Created with Stellarium

Does the full moon seem higher in the sky this month than July? It ought to. Last month’s moon was in the constellation Sagittarius the Archer, the same place the sun occupies during the month of December. It strode low across the southern sky peaking in the south a little more than two “fists” above the horizon here in Duluth, Minn. At the same time, the sun was in Gemini and as high in the sky as it gets for the year.

When we look at the full moon the sun is at our back. That’s why the moon appears opposite the sun in the sky, rising when the sun sets. Illustration: Bob King

Since that time, the sun has slid southward (lower) along its yearly path called the ecliptic as the season mellows to late summer. Because the full moon is directly opposite the sun and follows the same path, it moves northward or higher in the sky to keep pace with the sun’s decline in the south.

That’s why it’ll be higher in the sky tonight compared to June and July. The pattern continues until the winter solstice, when the full moon glares hard and white overhead in Gemini, while the sun shines meekly 180 degrees away in Sagittarius.

The sun’s path, shared by the moon and planets, is called the ecliptic. Because Earth’s tilted axis is tilted 23.5 degrees, the sun swings high and low along the ecliptic with the changing seasons. Click image to see an animated version. Credit: Durham University

If you’re game to watch a moonrise, click HERE to find when it cracks the horizon for your town tonight. Whatever the color, enjoy the sight.

2 Responses

  1. Miles Muzio

    Hi Astro Bob-

    Such an interesting astro-political event. This red-blue full moon happens between the two big political conventions in which red states and blue states are in a herculean struggle. Any big astronomical events in early November you see?

    1. astrobob

      Hi Miles,
      A colorful description of events! For November we’ve got a nice celestial grouping of the moon, Spica, Saturn and Venus in the dawn sky . There’s also a minor (penumbral) lunar eclipse on the 28th. And if we’re lucky a few Leonid meteors may zip by on the night of the 17th.

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