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Of all the planets in the Solar System the most beautiful of all is Saturn. On May 23rd the favourite planet reaches opposition and is therefore visible all night. Saturn starts the month continuing its retrograde motion in Scorpius before slowly moving into faint Libra on May 12th where it remains for the rest of the month. With a declination of –18 degrees it's better placed for Southern Hemisphere or tropical based observers where it appears higher in the sky and visible for a longer period of time.

At opposition, Saturn shines at magnitude +0.1 and is located 8.967 AU or approximately 1341 million kilometres (833.5 million miles) from Earth. Of course the spectacular rings are its most famous feature and even a small telescope will show them. They are currently wide open at a 24.4 degree tilt from our perspective. With an apparent diameter of 18.5 arc seconds and taking into account the rings, Saturn spans some 42 arc seconds across in total.

Through medium and large aperture scopes the rings are a fantastic breathtaking sight. In addition, a handful of Saturn's moons are also visible. The largest and brightest Titan shines at eight magnitude and can be seen with binoculars. In addition, small size scopes will also show other moons including Rhea, Tethys and Dione. Around opposition is a good time to look for moons of Saturn as they are also at their brightest for the year.

Saturn imaged by the Hubble Space Telescope  (NASA, ESA, and The Hubble Heritage Team (STScI/AURA))

A good opportunity exists to spot bizarre moon Iapetus just before opposition. 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 brighter than from the opposite side. This occurs on May 20 when Iapetus is at greatest western elongation and shines at magnitude +10.1, easily within the range of small scopes.

The chart below shows the position of Saturn in Libra at opposition. It's co-ordinates are R.A. = 15hr 59m 05s, Dec. = ??18d 18h 12s.

Saturn on May 23, 2015

Saturn on May 23, 2015 - pdf format