Why Is the Moon So Low (or So High)?

Moon

The Moon meets each planet the next two weeks—hovering right along side of it! So this is your chance to easily identify the planets. Plus, for all you Moon lovers, let’s answer why the Moon rides high or runs low in the sky? What does this mean and why does it happen? Find out from Almanac astronomer Bob Berman.

The Moon Meets Each Planet

We are now enjoying a jewel box of nightly gemstones. Unlike this past spring, all four of the most brilliant and easily-seen planets are well placed. But just to make things unnecessarily easy, the Moon is about to highlight each one by hovering alongside it. Mark the following on your calendar:

  • Just before dawn on September 14, the crescent Moon will hover right next to dazzling Venus, the Morning Star. If you miss it, no problem. There’ll be a repeat performance on October 13 and 14.
  • All night long, the gibbous Moon will float alongside Jupiter on September 24.
  • Also all night long, the gibbous Moon will hover near Saturn the next night, September 25.
  • The nearly Full Moon will sit extremely close to brilliant orange Mars on October 2. Mars will soon be brighter and closer than it will again appear until 2035. It’s that brilliant orange “star” that “rides high” these nights, and pops up in the east starting around 9:30. It’s still high at dawn.

See my September Sky Watch for more info about this month’s night sky.

Why the Moon Rides High or Low

Speaking of “riding high,” your letters show you care about the Moon’s position in the sky. Want to predict it for yourself? A quick two-step process lets you know whether tonight’s Moon will “ride high” or “ride low” across the sky.

Let’s first look at the Sun:

  • You may already know that in summer the Sun “rides high” but takes a low-down path across the sky every winter.
  • Around the March equinox and September equinox, like now, the Sun occupies an in-between position.

The Moon Mimics the Sun 

Well, if you know the current lunar phase, you can think of the Moon doing what the Sun does, in the following way:

  • Each month, the Full Moon travels oppositely from the Sun during that month. In early summer when the sun rides very high, that’s when the Full Moon rides at its lowest.
  • This September and October, the “opposite” of the Sun’s current equinoctial position is the other equinox, the one in March, which is identical.

Thus, September and October full Moons are unique in that they parade across the sky the same way as the Sun during those months. This is the only time when this happens.

Other phases? Different story. The first quarter Moon always behaves the way the Sun will, three months in the future. So during the next first quarter (half Moon) on September 23, expect it to match the Sun’s behavior three months later, in late December. That’s the lowest Sun of the year.

See the Moon phase calendar.

So there’s your answer:

The coming first quarter Moon will “ride super low” as it crosses the sky. And those conditions apply for a few days before and after each lunar phase. Also remember that low Moons are often more yellow or orange, and tend to look much larger, so there’s that, too.

Finally there’s the last quarter Moon, which is the other half Moon. We just had one, and the next will happen October 9. It always behaves like the Sun did three months in the past. Meaning, in early July. Thus it rides super high.

To review, the full Moon travels opposite from your current Sun—when the Sun rides high, the full Moon rides low. The first quarter acts like the sun will behave three months in the future. The last quarter Moon performs the way the sun did three months in the past.

Memorize all that and the Moon’s path across the sky will never be a surprise.

Why does the Moon look so big? Learn about the “Moon Illusion.”

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Source: Farmer's Almanac - Amazing Sky