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Looking Up column: Less seen, the waning moon

Peter Becker
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The sun, planets, dwarf planets and largest moons of our solar system are shown at scale for their relative sizes. [Photo by Beinahegut (Own work) [CC BY-SA 4 (https://creativecommons.org/licenses/by-sa/4)], via Wikimedia Commons]

We had a full moon on Oct. 1, and it was known as the harvest moon. October 2020 brings a second full moon, on Oct. 31. When this occurs, it is commonly called a blue moon.

It’s odd though, why the moon has no regular name. After all, the natural satellites around the other planets are also called “moons” and we have unique names for each.

Mars, so brilliant now as it approaches the closest approach to the Earth on Oct. 6 and opposition with the sun on Oct. 13, has two moons: Deimos and Phobos.

Jupiter, still shining bright in the south-southwest with twilight’s end, has four large moons, Io, Europa, Ganymede and Callisto. Jupiter has a host of smaller moons too, which we have named. You can see the four big ones easily in any size telescope.

Saturn is over to the left of Jupiter this fall. Its largest moon, Titan, is easily found in a three-inch or larger telescope, forever attending the ringed planet.

We sometimes call the moon “Luna” but that is merely Latin for moon.

Third-quarter moon is on Oct. 9, waning towards new moon on Oct. 19.

Each evening through this period, the moon rises later and later, giving us a longer time to see the stars without moonlight.

On the other hand, you need to wait up longer to see moonrise and enjoy the waning phases. This half of the moon’s orbit is the least well known to the public, as the moon is in the night sky when most are keeping an appointment with their pillow.

I must admit I have seen a lot less of the waning moon at night, especially near the third quarter and the thinning crescent as the moon slides towards the sun and its “new” phase.

You probably have seen the waning moon many times, in the morning after sunrise, the pale moon standing out in the blue sky.

When I do get to see it, I am all the more pleased.

Seeing the moon with eyes alone is always wonderful but the view in a telescope is a whole different experience. Any size telescope will show you the multitude of craters, big and small and many overlapping; rays of light material fanning from certain craters depending on how the asteroid hit so long ago; vast lunar mountain ranges; peaks within some craters; dark, hardened lava plains called maria (or “seas”) which give us the features of the Man in the Moon; cracks and rilles - dry channels.

Where sunlight meets dark we call it the terminator, where the sun as seen from the moon is low and casts long and deep shadows. The craters and mountains seem to stand out in relief as you peer through your telescope.

If you are used to this from seeing the waxing phases in the evening, leading up to the full moon, be sure to stay up some time and see the moon’s terminator after full phase. The sun comes in from the opposite direction, giving a whole new perspective.

Of course, you may as well know, the moon’s craters, mountains and maria are also named. You can find detail lunar maps, lunar atlases lined in longitude and latitude, and moon globes giving you this information.

I was just reading an amazing thing that I never considered before. Someone had the bright idea of adding together the diameter of each of the planets in our solar system, Mercury through Neptune, and comparing the total with the distance to the moon. Can you guess?

The planets, not counting Earth, totaled together at their equators, is approximately 247,054 miles. This is less than the maximum distance of the moon from Earth (called the apogee), 252,088!

Even with colossal Jupiter and Saturn, the planets would fit snug between the Earth and the moon!

Good thing the family of planets is socially distanced.

(The moon’s closest point, or perigee, incidentally, is 225,623 miles.)

The sun would not fit. At 865,370 miles wide, only about one-third would fit between Earth and moon and neither would last a second to measure it.

Be sure to enjoy the moon, planets and stars the next clear night. Near where I live, the moon rises around 7:53 p.m. Saturday, Oct. 3, and at last quarter phase, Oct. 9, it comes up about 11:44 p.m. Currently, the moon is in its waning gibbous phase.

The exact time of moonrise and moonset depends on your location.

Keep looking up at the sky!

Peter Becker is managing editor at The News Eagle in Hawley, Pennsylvania. Notes are welcome at news@neagle.com. Please mention in what newspaper or website you read this column.

The waning gibbous moon, after its full phase, photographed Aug. 28, 2010. [Photo by Craig Hurda (Own work) [CC BY-SA 3 (https://creativecommons.org/licenses/by-sa/3)], via Wikimedia Commons]