Moon Meets Four Planets September 11 to 19

Summer's Last Conjunctions

Sep 15, 2018
Waxing Crescent Moon

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Over the upcoming days, see the Moon visit four bright planets–for the last great conjunctions of this year! Most notably, mark your calendars for September 17 when the Moon shines close to Saturn’s upper left as darkness falls.

The Harvest Moon

Sure, everyone will focus on the Moon later this month. When it’s full on the 24th, it’ll be the Harvest Moon.  The Harvest Moon on September 24 is one of only two Full Moons with an official astronomical name. (The other is the Hunter’s Moon.)  Other Moon names come from Native American tribes or folklore. See what makes the Harvest Moon special.

But between now and then, you have the chance to see summer’s last conjunctions!  You won’t see such a rich bunch of evening sky conjunctions for the rest of the year, either.

Summer’s Last Conjunctions

If you missed the dramatic summer planet extravaganza, or even if you did not, here’s the best way to salute its fade-out. The ground rules are short and easy.

Simply go out when evening twilight is fading, around 7:30 P.M.

  • On the 12th, the crescent Moon floats above dazzling Venus.
  • On the 13th, the Moon stands above Jupiter.
  • On the 17th, the Moon shines closer to Saturn’s upper left at dusk. Mars is two or three fists to their left.
  • On the 18th, the Moon forms the top of a triangle with Mars to its left and Saturn to its right.
  • On the 19th, the Moon sits above Mars and the two travel across the southern sky together. Saturn almost three fists to their right or lower right. 

A solid week of striking conjunctions.

Next month when it again comes around in its orbit, one planet (Venus) will be gone, another (Mars) will only be half as bright, and a third (Jupiter) will be uncomfortably low.

So this is it. The Moon’s final great lunation of 2018.

September 17 to 19, 2018

If you have a backyard telescope, the best views of the Moon will be the 17th  to 19th, when its craters and mountains will be dramatically lit up with maximum contrast, like in a sci-fi movie.

The Moon, Saturn, Mars are highest as darkness falls; they may appear rather low in the southern sky from more northerly regions.

Ruddy Mars is brighter than golden Saturn. Both are visible with the naked eye. If you have a telescope, you’ll easily see Saturn’s rings.

As for the planets, you never go wrong with Saturn, whose rings are still optimally tilted toward us. People go, “Oh my God,” and “That’s not real!” when they see Saturn through a backyard telescope. Tip: The view is best on a night of steady air, which shows itself with untwinkling stars and, perhaps, a bit of haze.

Bottom line: September’s optimum sky-harvest doesn’t arrive with the Harvest Moon, but ahead of it.

About This Blog

Welcome to “This Week’s Amazing Sky,” the Almanac’s blog on stargazing and astronomy. Bob Berman, longtime and famous astronomer for The Old Farmer’s Almanac, will help bring alive the wonders of our universe. From the beautiful stars and planets to magical auroras and eclipses, he covers everything under the Sun (and Moon)! Bob, the world’s mostly widely read astronomer, also has a new weekly podcast, Astounding Universe

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