Saturn makes its triumphant return to the dusk sky.
It seems like most of the planets have fled the evening scene. 2025 sees a decided lack of planetary action after sunset, just when many observers are out skywatching. Jupiter hangs high at dawn, and the crescent Moon is making its sunward dive this week, towards a rare triple conjunction with Regulus and Venus on Friday the 19th. Mars is currently the sole planet in the evening sky, although it’s now receding from us, lost low in the murk of dusk. At least it has newly discovered comet C/2025 R2 SWAN and distant interstellar Comet 3I/ATLAS (passing 0.2 Astronomical Units from Mars on October 3rd) to keep it company.
But that’s about to change this week. Saturn reaches opposition on Sunday, September 21st, passing closest to the Earth at just over 8.5 Astronomical Units (AU) or 1.3 million kilometers distant, and rising opposite to the setting Sun. This marks the best time to view the ringed world, as it dominates the night sky from sunset until sunrise.
Saturn rising to the east at opposition. Credit: Stellarium.
Saturn in 2025
Opposition 2025 also occurs just 37 hours before the southward equinox on September 22nd. You can see the result as Saturn loiters near the March equinoctial point known as the First Point of Aries, now located in the astronomical constellation of Pisces the Fishes. This is where the Sun sits in March.
Shining at magnitude +0.6, Stately Saturn takes 29 years to orbit the Sun. In the pre-telescopic era, Saturn actually represented the edge of the solar system, a frontier beyond which lay the vault of the heavens.
Saturn’s Wobbling Rings
Seeing the rings of Saturn are always the highlight of any evening star party. Even a small 60mm refractor at low power will reveal the ring system. 2025 is also a special year, as the rings appeared mainly edge on as seen from the Earth. This cycle happens once every 14 years, and the rings are headed towards their widest tilt of 27 degrees open once again in 2032.
There’s also an annual wobble, due mainly to the orbit of the Earth. For example, even though the rings crossed edge-on on March 23rd 2025, they actually widened by about 5 degrees again this summer, and are near edge-on again at opposition before finally widening once more in to 2026. The southern hemisphere is now tipping towards us through the next 14 year cycle, before the rings are once again edge-on in 2039.
The changing tilt of Saturn’s rings as seen from the Earth. Image credit: Roger Hutchison.
At the eyepiece, the shadow of the planet on the rings disappears around opposition, as it’s cast straight back from our point of view. You may, however, still notice the thin ribbon of the ring system’s shadow cast back on the planet itself.
An enviable view of Saturn as captured by NASA’s Cassini mission. Credit: NASA/JPL-Caltech/SSI reprocessing by Kevin M. Gill/Thomas Thomopoulos.
The rings of Saturn are especially prone to a brightening around opposition. This is known as the Seeliger effect, also known as opposition surge. This occurs because the little snowball particles in the rings are all at 100% illumination around opposition, acting like little retro-reflectors free of shadow.
The Opposition Surge effect, seen in this series of images of 1 Ceres taken by NASA’s Dawn spacecraft. Credit: NASA/Dawn
You see this on other objects in the solar system as well. For example, the quarter phase (half illuminated) Moon has a magnitude of -10.4, though the Full Moon shines at a dazzling magnitude -12.4. That’s 2 full magnitudes or almost six times as bright for just double the apparent area.
Also, watch for Saturn’s retinue of moons shuffling back and forth from night to night. Saturn is currently the record holder in our solar system with 274 (!) known moons, though you’ll only see about half a dozen at the eyepiece.
The most conspicuous is +8th magnitude Titan, orbiting Saturn once every 16 days. Titan can actually cast a shadow on Saturn near ring plane crossing season, and is just now wrapping up such a cycle in 2025. We only have two more shadow events for Titan left: one on September 20th and another on October 6th, both favoring North America.
Looking outward into the solar system, +8th magnitude Neptune also reaches opposition this month, 2 days after Saturn on September 23rd. This bluish ice giant presents a tiny 2” disk, just 3 degrees north of Saturn. It’s strange to think: on a 165 year orbit, Neptune only just completed one orbit around the Sun in 2011 since its discovery in 1846.
Saturn versus Neptune near opposition. Credit: Stellarium.
Be sure to check out Saturn this weekend, as a harbinger to the fine season of planetary observing ahead to cap off 2025.