Saturn’s two-toned moon, Iapetus, sits 9.5’ west of the planet and shines at its brightest, offering a good chance to spot it.
At western elongation, Iapetus lies some 9.5’ west of Saturn, far beyond the orbits of the ringed world’s other visible moons. Credit: Stellarium/Oleg Pluton
- Saturn’s moon Iapetus exhibits greatest western elongation, positioned 9.5 arcminutes west of Saturn, presenting its brighter, icy hemisphere towards Earth, reaching a 10th magnitude brightness.
- Observational opportunities favor late evening or early morning hours, with Saturn reaching 25° altitude in the east around 11 P.M. local daylight time.
- Telescopic observation reveals Titan, Saturn’s brightest moon (mid-8th magnitude), 3 arcminutes east of Saturn; other moons, including Tethys, Rhea, and Dione, are also visible in close proximity to the planet and its rings, while Enceladus (12th magnitude) may be challenging to observe.
- Provided local times for sunrise, sunset, moonrise, moonset, and moon phase (waxing crescent at 45% illumination) are specified for 40° N 90° W.
Saturn’s moon Iapetus reaches greatest western elongation today, now located 9.5’ west of the ringed planet. Iapetus has two vastly different hemispheres, one light and one dark. As the moon orbits Saturn, it slowly rotates so that one and then the other side faces us, with its brightness varying vastly depending on which region is pointed at Earth. At western elongation the icy, brighter side of Iapetus is turned toward us, bringing the moon’s brightness up to 10th magnitude, in line with some of Saturn’s other moons (Rhea, Tethys, and Dione). Titan, at mid-8th-magnitude, is still brightest — we’ll make sure to locate it tonight, too.
Saturn is rising in the east about an hour after sunset. Give it a little time to climb out of the horizon haze and then point your scope at it late this evening or overnight into the early-morning hours. Around 11 P.M. local daylight time, it’s reached 25° in altitude in the east, hanging below the Circlet of Pisces and shining as the brightest point of light in that region of the sky.
Through a telescope, you’ll spot Titan some 3’ east of Saturn; again, it’s the brightest of the planet’s moons. Then look far — a full 9.5’! — west of Saturn to spot 10th-magnitude Iapetus. Much closer in, around midnight EST you’ll also see Tethys just off the eastern end of the rings, with Rhea just north of the rings also to the planet’s east. Dione lies west of the western edge of the rings, with much fainter (12th magnitude) Enceladus between it and the edge of the rings. You may not be able to spot Enceladus, so don’t be surprised if you can’t make it out.
Sunrise: 6:26 A.M.
Sunset: 7:34 P.M.
Moonrise: 1:56 P.M.
Moonset: 10:58 P.M.
Moon Phase: Waxing crescent (45%)
*Times for sunrise, sunset, moonrise, and moonset are given in local time from 40° N 90° W. The Moon’s illumination is given at 12 P.M. local time from the same location.
For a look ahead at more upcoming sky events, check out our full Sky This Week column.
