Everyone knows about the sudden change in sunset times every hour on the clock with the resulting early darkness when we go back to standard time in early November.
But now there is a gradual loss of daylight.
Between September 1 and the end of the month, we lose an hour of daylight. We lose a little over an hour in October. This slow loss of daylight leads to the shortest daylight period of the year – the winter solstice on December 21 – when Fayetteville’s daylight period is as short as nine hours and 48 minutes.
September also comes with the autumnal equinox on September 22, which marks the beginning of fall in the northern hemisphere and spring south of the equator.
The equinox means “equal night” and the hours of the day and night are assumed to be equal in length at the equinox.
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Only they are not.
An examination of Fayetteville sunrise and sunset times on September 22 at 7:03 a.m. shows the sunrise time with sunset at 7:14 p.m., so the two events are not exactly 12 hours apart.
We have to wait until September 27 before we have nearly 12 hours between sunrise and sunset. On that day, sunrise comes at 7:07 a.m. with sunset at 7:06 p.m. The moment of sunrise is the time when the upper edge of the sun breaks the horizon.
The problem is our atmosphere, which has a lens effect when the sun is at or near the horizon. The atmosphere bends sunlight and tends to “raise” the sun above the horizon higher than it should. The same effect slows down sunsets as the sun appears a little higher than it should be before it finally sets.
The length of Fayetteville’s day on that “most equal day,” September 27, is 11 hours and 59 minutes. This date is called “equilibrium” and varies depending on the latitude of the location at which sunrise and sunset occur.
The spring and autumn equinoxes are also the only times when the sun rises completely in the east and sets completely in the west.
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You can create and print an accurate calendar of sunrise, sunset, day length and twilight times for any month from anywhere at www.sunrisesunset.com.
And about this switch from DST early on Sunday, November 6th.
We, amateur astronomers, look forward to that date because the stars come out an hour before they appear. We’re not a fan of switching to DST in the spring because it gets late in the dark.
Jupiter in the evening
After spending most of 2022 in the morning sky, Jupiter reaches opposition on September 26. Opposition means that the planet is opposite the sun in our sky, rises at sunset, and is visible all night long. It is also the date on which Jupiter is closest to us.
You’ll notice the bright planet rising on clear nights now in the east after dark. It joins Saturn in the evening sky that now climbs into the southeast sky as darkness falls.
Besides Saturn, Jupiter is perhaps the next most interesting planet that can be observed with a small telescope.
Most telescopes magnified 30 times the appearance will show the bands to Jupiter due to its clouds and regions. Jupiter’s “mashed up” appearance is also evident due to its rapid rotation. The gas giant planet rotates once in less than 10 hours. This causes Jupiter to bulge at the equator so that it appears more oval than circular.
They also appear in small bands, the four largest moons on Earth. Galileo discovered the moons of Europa, Ganymede, Callisto and Lu in the early 17th century.
On Jupiter’s opposition night on September 26, Ganymede will appear on Jupiter’s eastern side while the moons Io, Europa, and Callisto will line up and surround the planet on the western side.
Telescopes 4-6 inches in diameter would show Jupiter’s famous “Big Red Spot” if the feature were on the Earth’s side. The slick is a massive storm that was raging on Jupiter as early as the 17th century when it was first observed by primitive telescopes. In large telescopes, Jupiter’s cloud belts display an array of interesting details and colours. Every once in a while, one of the larger moons passes between us and Jupiter, casting a shadow over the tops of Jupiter’s cloud.
Jupiter appears near the upper right of the moon on the night of September 11th.
If it’s cloudy on the night of Jupiter’s opposition, don’t worry about missing out on the show. The planet will remain with us in the evening sky until March 2023.
If you have a question about astronomy, send it to Backyard Universe, PO Box 297, Stedman, NC, 28391 or email email@example.com.