Monthly sky – September 2025

Here are some details on the Moon’s different phases, close approaches of planets and other astronomical events to watch for during the month of September.

September 5: The Moon at aphelion (92%), its greatest distance from the Sun – 152,457,150 km – at 5:32 a.m. EDT.

September 7: Full Moon (100%) – 2:08 p.m. EDT.

September 8: Conjunction – Close approach: the Moon (97%) – Saturn (mag: +0.62) visible as soon as the Moon rises in the east (at sunset) and throughout the night: the two heavenly bodies follow in each other’s path, taking a beautiful walk from east to west, from sunset to sunup. A breathtaking spectacle. Saturn is located to the right of the Moon.

September 10: The Moon at perigee (90%) – the closest distance from the Earth (356,500 km) at 8:09 a.m. EDT.

September 12: Conjunction – Close approach: the Moon (75%) –- open cluster M45 (the Pleiades). Now it’s young-star open cluster M45’s turn to join in the game of walking beside the Moon. Visible from 10:00 p.m. EDT at sunrise. M45 will be at the top right of the Moon.

September 13: Mercury at superior solar conjunction. End of Mercury’s appearance in the morning sky, plus its transition over the coming weeks to becoming an evening object. Too close to the Sun to be observed (dangerous).

September 14: Last Quarter Moon (50%) – 6:33 a.m. EDT.

September 16: Conjunction – Close approach: the Moon (30%) - Jupiter (mag: -2.05). After Saturn and M45, this time Jupiter will dance with the Moon. Located under the Moon when it rises in the east starting at 1:00 a.m. on September 16, Jupiter will follow the Moon until the sun rises. A spectacular duo you won’t want to miss.

September 19: Conjunction – Close approach: the Moon (6%) - Venus (mag: -3.91). Venus won’t be denied in this celestial ballet. On the heels of Saturn, M45 and Jupiter, the Venus and slender crescent Moon duo will dazzle us early in the morning of September 19. Visible to the east beginning at 4:45 a.m. EDT, this duo will be the showstopper of planetary encounters with the Moon this month.

September 21: New Moon (0%) – 3:55 p.m. EDT.

September 22: Autumn equinox at 2:20 p.m. EDT

September 23: Neptune is at opposition (mag: +7.68). Ideally positioned to be observable for much of the night with a small telescope. It is located just above Saturn all month and follows it closely.

September 24: The Moon at perihelion (4%) – its closest distance from the Sun (149,597,871 km) at 5:45 p.m. EDT.

September 26: The Moon at its peak (22%) – its greatest distance from the Earth (406,700 km) at 5:45 a.m. EDT.

September 29: First Quarter Moon (50%) at 7:54 p.m. EDT.

Happy skywatching!