Updated

Updated · National Geographic · Aug 27

September Sky Brings 9 Events, as Venus Hits -4.8 and Harvest Moon Rises Sept. 26

Updated

Updated · National Geographic · Aug 27

September Sky Brings 9 Events, as Venus Hits -4.8 and Harvest Moon Rises Sept. 26

Q: As September begins, what rare planetary disappearing act might you witness if you look up at the exact right moment?

If you look up at exactly the right moment, you might catch a lunar occultation — the Moon briefly making a planet seem to disappear. In early September, the most likely example is Jupiter on September 8. The main skywatching forecast highlights the Moon meeting Jupiter before sunrise, and supplemental astronomy sources note that in some parts of the world the Moon may actually pass directly in front of Jupiter, hiding it from view for a short time. A second rare disappearing act may come on September 14, when the thin crescent Moon passes near Venus after sunset. Some regions are expected to see an occultation of Venus as well, meaning the brightest evening planet could suddenly vanish behind the Moon’s edge and then reappear later. Whether you can witness either event depends entirely on location and timing. These occultations are not visible everywhere, and in some places one may occur in daylight or too close to the horizon for easy viewing. But if you are in the right region and watching at the precise moment, the “disappearing planet” to watch for at the start of September is Jupiter — with Venus offering a second chance later in the month.

Q: Will the glowing orange Harvest Moon completely ruin your chance to spot a distant ice giant hiding in the dark?

No—the Harvest Moon will make Neptune harder to spot, but it will not completely ruin the chance. Neptune reaches opposition on September 26, the same day as the full Harvest Moon. That is actually Neptune’s best annual window because the planet is closest to Earth, up all night, and at its brightest for the year, around magnitude 7.8. The catch is that Neptune is still far too faint for the naked eye, so binoculars or, better, a telescope are needed. The Moon’s bright glow will wash out many faint stars and reduce contrast, especially soon after moonrise when the orange full Moon is low on the horizon in Pisces. That makes star-hopping to Neptune more difficult. But Neptune itself will still be there, near the Moon and Saturn in Pisces, and experienced observers using a telescope should still be able to find it. The best strategy is to avoid the brightest moonlit period if possible. Try later in the night, after the Moon climbs higher and its orange horizon glow fades, or observe on nights a few days before or after September 26, when Neptune remains near peak visibility but moonlight is slightly less disruptive. A finder chart or sky app will be especially useful because the full Moon will hide many faint guide stars. So the Harvest Moon hurts deep-sky viewing much more than it hurts a targeted Neptune hunt. For casual observers, yes, it complicates things. For prepared observers with optics, Neptune remains within reach.

3 articles · Updated · National Geographic · Aug 27

Nine September sky events are lined up, led by Venus reaching its brightest evening magnitude of -4.8 on Sept. 18 and the full Harvest Moon peaking just before 1 p.m. ET on Sept. 26.
Sept. 6-8 opens with moon alignments with Mars and then Jupiter before dawn, while Sept. 14 brings an easier evening pairing as a crescent moon appears within 5 degrees of Venus after sunset.
Sept. 11-12's new moon will deliver the darkest skies of the month, improving views of galaxies, nebulae and one of the Northern Hemisphere's last chances in 2026 to see the Milky Way core.
Sept. 22's autumn equinox could also lift aurora odds, as Earth's tilt around the equinox often creates more favorable solar-wind conditions, especially at Arctic latitudes.
All month, observers can also target the Andromeda Galaxy around midnight to 1 a.m. local time, best seen from dark sites with binoculars or a small telescope.