SKY GUIDE:  This chart represents the sky as it appears over Maine during September. The stars are shown as they appear at 10:30 p.m. early in the month, at 9:30 p.m. at midmonth and at 8:30 p.m. at month’s end. Saturn and Jupiter are shown in their midmonth positions. To use the map, hold it vertically and turn it so the direction you are facing is at the bottom.

September marks the beginning of autumn for us in the northern hemisphere. After another long, hot summer, this will happen at exactly 3:50 a.m. on Monday the 23rd. That day, along with the spring equinox around March 22, can serve as unifying events for everyone on Earth once you become aware of what happens on those two days.

On only those two days each year, the sun rises due east and sets due west for everyone. Within a few days of those two important turning points, everyone on Earth also will experience 12-hour days along with 12-hour nights. The lag time happens because we orbit in ellipses and our axis is tilted at 23.5 degrees. So this is a good time twice a year to obtain a clearer window into the larger scale motions of our planet.

Another innovative way to see that is simpler and can be done twice every day, not just twice a year. Because the sun never really rises and sets, it’s merely an illusion created by the earth always spinning toward the east, you can think of every sunrise as “sunsight” and every sunset as “sunclipse.” We are just seeing the sun again every morning as the earth with everyone and everything on it continually spins toward the east; at this latitude, that happens at a good clip of 750 mph, or the speed of sound, and then every evening we see our own shadow eclipse the sun again.

Buckminster Fuller, a 20th-century futurist, first proposed those terms, and I find them very helpful to better understand what’s really happening all the time. Another great concept he introduced relates to stairways. Every time you walk up stairs, think of going “out stairs,” and every time you walk down stairs, think of going “in stairs.” The idea is you are really walking out from the center of the earth when you walk upstairs, and you are going in toward the center of the earth when you walk downstairs. Using this terminology gives you a better grasp on the concept of gravity, and the size and scale of the earth; just by changing your language, many other new and important insights also may dawn on you.

Every night as we plunge deeply into our own shadow, the gas giants Jupiter and Saturn remain the stars (pun intended) of the nightly drama that is our window into the universe, shielding us from the overpowering light of our daystar, commonly known as the sun, although there is nothing common about it. This reminds me of a profound line from Henry Beston’s book, “The Outermost House,” written in 1927, when he spent a year alone on a beach in Cape Cod.

“As the great earth, abandoning day, rolls up the deeps of the heavens and the universe, there opens a new window to the human spirit,” he wrote, “and few there be so clownish that some awareness of the mystery of being does not touch them as they gaze.” What an awe-inspiring and reverent way that would be to approach every amazing night of star gazing.

Jupiter is still in Scorpius but is moving in its normal, eastward or prograde motion again away from the orange giant star named Antares. By the end of the month it will set by 10 p.m. Move one constellation to the east and you will find golden Saturn hanging out in Sagittarius. Notice that Saturn is about 10 times fainter than Jupiter, and is also about twice as far away as Jupiter, at nearly a billion miles, or over an hour at the speed of light. Saturn will end its retrograde motion on the 18th, just a few days before fall starts. Through a telescope you will notice that its rings are still nicely tilted open at 25 degrees. Both planets are getting a little smaller and fainter because they are again retreating from Earth in their slower orbits, but for all of this month and next they remain two bright beacons in our evening sky.

During the first week of this month, the waxing crescent and gibbous moon will make a nice trek across the sky close to Jupiter and Saturn. It will be close to Jupiter on the 5th and 6th, and close to Saturn on the 7th and 8th.

Venus finally will reappear very low in our western evening sky late this month after a prolonged absence due to its superior conjunction with the sun as far away from the earth as it can get. This amazing planet is about the same size as Earth and is called our sister planet, but that’s where all similarities end. It is a permanent 900 degrees on its surface, and its day is longer than its year because it only spins at about 4 mph, which is walking speed. It also spins in retrograde, so the sun would rise in the west every day, but one day equals 243 earth days and one year equals 225 earth days.

Mars won’t show up again until late October in the morning sky. It’s now about as far away as it can get from us at superior conjunction on the other side of the sun.

Neptune is at opposition this month on the 10th in the constellation of Aquarius, two constellations to the east of Saturn, but you’ll need a small telescope or a good pair of binoculars to spot it. Johan Galle, a German astronomer, gets partial credit for discovering this last planet 173 years ago on Sept. 23, 1846, the only planet in our solar system that was first predicted mathematically, then was found very close to where it was supposed to be. Since its discovery, Neptune has completed just one orbit around the sun; it takes 165 years for Neptune to orbit the sun. Pluto, at 248 years, is in an exact 3 to 2 resonance with Neptune, which is common for several other planets.

Sept. 3: Viking 2 landed on Mars on this day in 1976.
Sept. 5: The first quarter moon is at 11:12 p.m.
Sept. 6: The moon is near Jupiter tonight.
Sept. 7: The moon is near Saturn tonight and tomorrow night.
Sept. 11: A spacecraft named International Cometary Explorer made the first flyby of a comet on this day in 1985. It continued on to make a flyby of Halley’s Comet the next year.
Sept. 14: The full moon, also known as the Harvest Moon, is at 12:34 a.m. This full moon will rise a little later each night, about a half-hour instead of the average of 55 minutes, and it will look full for five days. Why? Because the angle of the ecliptic with our horizon is at its most shallow this time of year for us in the northern hemisphere.
Sept. 17: On this day in 1789, William Herschel discovered Mimas, one of the brighter moons of Saturn. It’s 250 miles in diameter and has a giant crater with a four-mile high central peak that covers one third of this moon.
Sept. 20: A waning gibbous moon will pass close to Aldebaran and the Pleiades in Taurus this morning around 6 a.m.
Sept. 21: The last quarter-moon is at 10:42 p.m.
Sept 23: The autumnal equinox is at 3:50 a.m.
Sept. 26: A slender waning crescent moon will pass close to Regulus in Leo this morning, one hour before sunrise.
Sept. 28: The new moon is at 2:27 p.m.
Sept. 29: Enrico Fermi, who helped develop modern quantum theory, was born on this day in 1901. The particle accelerator in Illinois, Fermi lab, is named after him. He won the Nobel Prize in physics in 1938 for discovering principles that led to nuclear fission.

Bernie Reim of Wells is co-director of the Astronomical Society of Northern New England.