Saturn's bizarre two-tone moon Iapetus reaches greatest western elongation on September 9, 2016, visible in small scopes

Saturn, mag. +0.5, is currently an evening object in the constellation of Ophiuchus. The planet famous for its spectacular ring system is visible towards the south-southwest from northern latitudes or towards the northwest from southern latitudes as soon as it's dark enough. Currently in the same region of sky is Mars (mag. -0.2) and red supergiant star Antares (α Sco - mag. +1.0). In addition on September 8th and 9th, the Moon passes just north of the the planets.

Mars and Saturn during September 2016 - pdf format (credit:- freestarcharts)

Saturn has many moons that are visible in telescopes. One peculiar example is Iapetus, a world famous for its "two-tone" colouration with one side much darker in colour than the other. As a result, when positioned on the western side of Saturn, as viewed from Earth, it appears much brighter than on the eastern side.

On September 9th, Iapetus reaches greatest western elongation and therefore at its brightest. At magnitude +11.5, it can be seen with a small scope of 80mm (3.1-inch) aperture. However, since the Moon is nearby a larger scope maybe required this time.

The diagram below shows the position of Saturn and its brightest Moons visible on September 9th when Impetus reaches greatest western elongation. Note the wide separation of Iapetus. For comparison, Titan (mag. +8.8) is located 1.4 arc minutes from Saturn whereas Iapetus is 8.2 arc minutes away.

See also

The Planets this Month - September 2016