Titan's shadow crosses Saturn as the planet offers up its best views of 2025 this weekend

The vast shadow of Saturn's largest moon Titan will fall upon the upper extreme of the ringed gas giant in the early hours of Sept. 20, just one night before the planet shines at opposition in Earth's sky.

Once every 15 years, the orbital mechanics of the solar system brings the orbital path of Titan into an edge-on alignment with Earth, opening a brief window during which the moon's colossal shadow can be spotted periodically sweeping across the surface of the gas giant.

The next Titan shadow transit will begin at 1:09 a.m. EDT (0509 GMT) on Sept. 20, at which time the vast umbral silhouette will be visible on the upper left of the gas giant's disk, with the moon itself positioned just below, according to Sky & Telescope. Titan's dark footprint will take a little over two hours to traverse left to right across Saturn's cloud tops, before finally fading from view at 3:34 a.m. EDT (0734 GMT).

Saturn can be found shining high in the eastern sky, below the stars of the constellation Pisces as the transit begins on Sept. 20. However, you'll need a telescope with an aperture of 8-inches or more at 200X magnification to get a good view of the moon's shadow under decent atmospheric conditions, according to Hayden Planetarium instructor and lecturer Joe Rao.

If you don't have an instrument capable of resolving Titan's vast lunar shadow, there's absolutely no need to despair. Saturn will reach opposition, the point at which it appears opposite to the sun in Earth's sky, at At 1:37 a.m. EDT (0537 GMT) on Sept. 21, marking a perfect opportunity to explore the gas giant with either your eyes, binoculars or through the eyepiece of a telescope.

Saturn is at its brightest and closest to Earth during this time, which may make the world appear fractionally larger through the eyepiece of a telescope compared to when it is at a more distant point in its orbit.

The gas giant will be visible from sunset to dawn for viewers in the U.S. around opposition, providing ample opportunity to explore subtle variations in the cloud surface of the gigantic world. A larger telescope will also provide a fascinating view of Saturn's rings, which will appear as a bright line bisecting Saturn's amber disk, with the delicate structures visible in previous years hidden from view by its edge-on alignment.

Titan's final shadow transit is set to take place on Oct. 6 later this year. Stargazers hoping to see the event for themselves should check out our guide to the best telescope deals going in 2025.

Editor's Note: If you capture an image of the Titan shadow transit and want to share it with Space.com's readers, then please send your photo(s) along with your name, location and comments about your shoot to spacephotos@space.com.