September's full Moon is typically known as the "Harvest Moon."
Each Monday I pick out the northern hemisphere’s celestial highlights (mid-northern latitudes) for the week ahead, but be sure to check my main feed for more in-depth articles on stargazing, astronomy, eclipses and more.
What To Watch For In The Night Sky This Week: September 20-26, 2021
This week it’s all about the full “Harvest Moon,” surely the most well-known apparition of our natural satellite. Traditionally named because its all-night light is said to help farmers get their harvests in (though nowadays surely they use huge floodlights?), the iconic name actually has less to do with crops and more do with this week’s fall or autumnal equinox—or “equal night.”
The “Harvest Moon” is always the closest full Moon to that important seasonal way marker, which indicates when the Sun crosses the celestial equator heading south to create shorter, cooler days as the northern hemisphere begins to tilt away from our star.
Here’s everything you need to know about stargazing and the night sky this week:
Monday, September 20, 2021: A full ‘Harvest Moon’
At 23:55 UT today sees perhaps the most famous full Moon of them all—the “Harvest Moon.” The prize is to see it appear in the eastern horizon draped in autumnal oranges and yellows.
If there are clear skies then look due east about half an hour after sunset or get the exact times of moonrise and moonset for your location. Be patient—it will appear!
A "Harvest Moon" rises over government landmarks Lincoln Memorial, the Capitol building and the ... [+]
Tuesday, September 21, 2021: A second chance ‘Harvest Moon’ plus Mercury and Spica
Tonight offers another opportunity to see the full “Harvest Moon” rise into a twilight sky. The action will happen in the eastern sky a little later than yesterday, so in a deeper twilight. Check the the exact times of moonrise and moonset for your location.
Meanwhile, in the west, the smallest planet (Mercury) and the brightest star in the constellation of Virgo (Spica) will be in conjunction right after sunset, separated only by about 1°. It will be a tricky find since they’ll both likely be lost in the mirk of the horizon. Good luck!
Tuesday, September 21, 2021: Mercury and Spica in the western sky just after sunset.
Wednesday, September 22, 2021: Fall equinox
At precisely 19:21 UT today it’s the fall or autumnal equinox. It marks the point when the midday Sun is directly above the equator, giving every location on the planet 12 hours of daylight and 12 hours of darkness.
The Sun will rise due east, follow an arc right along the celestial equator and set due west. It’s also known as the southward equinox.
Thursday, September 24, 2021: Moon and Uranus
Thursday, September 24, 2021: Moon and Uranus
A 84%-lit waning gibbous Moon will tonight be a mere 1º from the planet Uranus, which makes it a good time to try to spot the seventh planet from the Sun about 1.8 billion miles distant—though you’ll probably need binoculars.
Sunday, September 26, 2021: Moon in Taurus
Sunday, September 26, 2021: Moon in Taurus
After midnight and into the pre-dawn hours a 76%-lit waning gibbous Moon will slide between the beautiful Pleiades and the Hyades star clusters in the constellation of Taurus.
Look high in the southwest before dawn for these jewels of the night sky that are soon to be post-sunset objects—and with us all winter!
Albireo is the most well known “double star” of all.
Star of the week: Albireo
Albireo, Beta Cygni, is surely the most well known “double star” of all, but to see this, the head of Cygnus, “The Swan” in summer skies, does require a small telescope at 30x power.
Line it up and you’ll see Albireo A (a golden color) and Albireo B (a less bright blue) contrast each other—it’s a spectacular sight!
Sagitta, the arrow
Constellation of the week: Sagitta, the arrow
One of the smallest constellations in the sky, Sagitta is made from stars shaped like an arrow—two at the tail, one in the center and another at the point. You’ll find Sagitta about 10° above Altair at the foot of the famous “Summer Triangle” asterism high in the night sky this month. The darker the skies, the easier it will be to find Sagitta.
Times and dates given apply to mid-northern latitudes. For the most accurate location-specific information consult online planetariums like Stellarium and The Sky Live. Check planet-rise/planet-set, sunrise/sunset and moonrise/moonset times for where you are.
Wishing you clear skies and wide eyes.
