September 2025

Total lunar eclipse

We have a total lunar eclipse this month. On the 7^th Universal Time, Africa,Europe, Asia, Australia, and the Pacific Ocean get to see at least part of it. Parts of eastern Brazil and western Alaska do too. Everywhere else in the Americas will be on the wrong side of the earth for this event. The hard-to-see penumbral phase starts at 15:28. At 16:27, the partial phase starts. Then totality is at 17:31. Greatest eclipse is at 18:12. Totality ends at 18:53. The partial phase is over at 19:56. And the penumbral phase ends at 20:55. This will be a moonrise event for that slice of Brazil, the Atlantic, Africa, and Europe. It happens at moonset for Australia, the Pacific, and far east Asia, plus that part of Alaska.

Partial solar eclipse

On the 21^st Universal Time, the moon passes in front of the sun. The moon’s umbral shadow cone passes too far south of Earth for a total phase. Observers in New Zealand, Fiji, and Vanuatu get a sunrise event. Other parts of the southern Pacific get a complete event from partial phase beginning to ending. Greatest eclipse is of magnitude 0.855 close to eastern Antarctica. Remember to protect your eyes with safe solar viewing filters or a safe projection method to see this eclipse.

Other events

Right after sunset, Mars is marching on a path that will go by Spica in Virgo as the middle of the month approaches. It will be a little hard to see from the northern hemisphere as the planet and constellation sink lower into the sunset. You need a clear horizon to the west. The view is easier from the southern hemisphere where you also get Mercury very close to the horizon at dusk in the last few days of the month. The moon passes near Spica on the 24^th and Mars the next evening.

Don’t confuse orange Arcturus for Mars in the evening sky. The bright star at the bottom of Boötes is higher up than Mars at dusk.

Most observers will see Saturn rising at dusk. The ringed planet will be at opposition on the 21^st, 8.55 astronomical units from us. Neptune is nearby and is at opposition on the 23^rd. Its distance is 28.9 a.u.!

Uranus rises in late evening. It’s still hanging out between the Pleiades and the Hyades.

Early morning riser Jupiter starts the month near Wasat in Gemini. The big planet will appear closest to the star on the 6^th and 7^th. The moon passes by on the 16^th. At month’s end, Jupiter hasn’t gotten much farther along and is on still on the east side of Gemini.

Closer to dawn, Venus rises, starting September near Asellus Australis in Cancer. Venus marches on into Leo and is closest to Regulus on the 19^th and 20^th. The moon passes by them at the same time. The planet has made it most of the way toward the lion’s back feet as September ends.

Some observers can find Mercury approaching Regulus early in the month. The messenger planet passes the star on the 2^nd. Low northern latitudes get the best view, but even from there the pair are very close to the horizon with the sunrise glow getting bright. Mercury’s headed to superior conjunction on the 13^th. After that, you can look for Mercury to reappear in the evening if you’re at a low southern latitude. A young moon will be close on the 22^nd, but that won’t really help. Both will be lost in the sunset glow.

The moon

On its way around the celestial sphere this month, the moon begins at southern lunistice on the 1^st at 28.6° south of the equator. It’s just after first quarter phase that day. Of course, it’s full on the 7^th, the date of the aforementioned total lunar eclipse. On the 8^th, Luna crosses the equator going north. It’s 3.5° from Saturn and 2.5° from Neptune the same night. Lunar perigee is on the 10^th at 364,700 km away. The moon passes 5.2° from Uranus on the 12^th. Northern lunistice is on the 14^th. The moon will be 28.6° from the equator. On the 16^th, Luna passes 4.5°from Jupiter and 2.4° from Pollux. The Venus-moon pairing for the month is on the 19^th at 0.7° separation. The moon will also pass 1.2° from Regulus that day and Venus will be 0.5° from the star. It’s across the equator going south on the 21^st, the same day as new moon and the solar eclipse. Then the moon’s 2.5° from Mercury on the 22^nd, 1.0° from Spica on the 23^rd, and 3.6° from Mars on the 24^th. Apogee is on the 26^th at 405,600 km away. We have 0.6° from Antares on the 27^th. And on the 29^th, a second southern lunistice occurs at 28.6°.

Occultations this month include El Nath on the 14th and Antares on the 27th.

Equinox

The equinox happens on the 22^nd at 18:20 UT. The sun will be over the equator going south.