September is one of the best months of the year for stargazing in the northern hemisphere. Not only do the nights get longer and begin earlier as Earth reaches its equinox later in the month, but for many, temperatures will remain warm enough for shirt-sleeve sky-watching in the early evening.
Equinox on Sept. 22 puts Earth side-on to the sun, a favorable alignment for the solar wind to create geomagnetic storms in Earth’s magnetic field—which could mean displays of the northern lights at lower-than-usual latitudes. Elsewhere you can watch a “supermoon” be eclipsed, with the added the prospect of a naked-eye comet later at month’s end.
Here are the stargazing, moon-watching and night sky highlights for September 2024:
Venus And A Crescent Moon
When: after sunset on Tuesday, Sept. 3-Thursday, Sept. 5.
Where: western sky.
It’s the sight sky-watchers have longed for all year—a bright Venus in the post-sunset sky close to a delicate-looking crescent moon. Beautiful!
On Tuesday and Wednesday, after sunset, look west to spot the super-slim 1%-lit crescent moon and the 3%-lit waxing crescent moon, respectively. Binoculars may be needed, particularly on Tuesday. Come Thursday, a brightening 7%-lit crescent moon will be visible in the western sky, appearing to the left of Venus.
Saturn At Its Biggest And Best
When: after sunset on Saturday, Sept. 7.
Where: eastern sky.
Tonight, Saturn will be at its annual opposition. That means it’s the biggest, brightest and best for the year, rising in the east at sunset and sinking in the west at sunrise. This is due to Earth passing between Saturn and the sun every 378 days.
Tonight, and each night for the next few weeks, is the perfect time to observe the ringed planet through any telescope (without one, you’ll not see its rings).
The Big Dipper ‘Falls Down’
When: after sunset on any clear night in Sept.
Where: north-northwest sky.
This month, the position in the sky of Big Dipper, also known as the Plough, reveals the changing of the seasons. The famous asterism, or shape (not a constellation), consists of seven bright stars, with Alkaid at the top of the handle and Dubhe at the bottom of the bowl. Like Cassiopeia, opposite, it is circumpolar (always visible) in the northern night sky. Its low position after dark indicates that it’s autumn—as in the memory aid for the Big Dipper: “Spring up, fall down.”
‘Super Harvest Moon Eclipse’
When: moonrise (dusk) on Tuesday, Sept. 17.
Where: eastern sky.
The “Harvest Moon,” famous for aiding late-night crop gathering in September, will tonight appear as a big, brighter “supermoon” near Saturn. That’s not the half of it. A partial lunar eclipse will also occur tonight, and it will be visible in North and South America, Europe, Africa, and the Middle East. In North America, the best time to see the spectacle is during the moonrise, while in Europe, it’s when the full moon is high in the sky. Saturn will be easily visible wherever you are about 30 minutes after moonrise as the sky darkens.
The Northern Lights
When: close to Sunday, Sept. 22.
Where: northern sky.
The Northern and Southern Lights are most intense around the equinoxes, making the weeks surrounding Sept. 22 a great time to visit the Arctic Circle for potential aurora displays. However, given May 10’s sudden solar “superstorm” and strong displays since at exceptionally low latitudes—mostly thanks to the sun’s once-in-11-years “solar maximum” this year (or early next)— it may be wise to choose a dark sky destination to escape to if and when a G5 geomagnetic storm is forecast.
A Naked-Eye Comet?
When: before sunrise on Monday, Sept. 30-Wednesday, Oct. 2.
Where: eastern sky.
Are we about to see a brilliant naked-eye comet? It’s possible but hard to predict in advance. What we do know is that there is a chance that Comet C/2023 A3 (Tsuchinshan-ATLAS) will be visible at the end of September shortly before sunrise. For observers in the northern hemisphere, look east just before sunrise. On Monday, a 5%-lit waning crescent moon will accompany the comet, followed by a lower-hanging 2%-lit crescent on Tuesday, with a dark sky on Wednesday. Come mid-Otober, the comet‚ if it survives that long—could be visible after sunset.
The times and dates given apply to mid-northern latitudes. For the most accurate location-specific information, consult online planetariums like SkySafari Pro, Stellarium and The Sky Live. Check planet-rise/planet-set, sunrise/sunset, and moonrise/moonset times to see where you are.
Pick up my books Stargazing in 2024, A Stargazing Program For Beginners, and When Is The Next Eclipse?
Wishing you clear skies and wide eyes.
