Saturn's bizarre two-tone moon Iapetus reaches greatest western elongation on August 6, 2015, visible in small scopes

Saturn, mag. +0.4, remains well placed for observation amongst the stars of Libra during August. The beautiful ringed planet has just resumed direct motion once more and is visible as soon as it's dark towards the southwest (Northern Hemisphere) / northeast (Southern Hemisphere) before setting around or just after midnight. With a declination of -17 degrees it's better situated from southerly latitudes, appearing higher in the sky.

Saturn during August 2015 - pdf format

At the beginning of the month and particularly on the evening of August 6th a good opportunity exists to spot peculiar satellite Iapetus. This world is famous for its "two-tone" colouration with one side being much darker in colour than the other. As a result, Iapetus when positioned on the western side of Saturn (when viewed from Earth) appears much brighter than on the eastern side.

On August 6th, Iapetus reaches greatest western elongation and therefore at it's brightest. At magnitude +10.1, it can be seen with a small scope of 80mm (3.1-inch) aperture. The diagram below shows the position of Saturn and it's brightest Moons visible on August 6th. Note the wide separation of Iapetus. For comparison, Titan (mag. +8.7) is located 1.3 arc minutes from Saturn whereas Iapetus is 8.3 arc minutes. By August 25th, Iapetus fades to eleventh magnitude and moves to 2.1 arc minutes north of the planet.