Planet Saturn, undisputed jewel of the Solar System, was at opposition on 23 May in the constellation Libra. It was then closest to Earth for 2015 at a distance of 8.97 astronomical units (AU), or 834 million miles (1,341 million kilometres). Five weeks later, the ringed planet attains a maximum altitude of just 18 degrees above the southern horizon for the centre of the British Isles at the end of civil twilight, which is around 10:30pm BST.
In the last days of June, Saturn’s distance from Earth has increased somewhat from opposition, the gulf between our two worlds now standing at 9.16 AU, or 852 million miles (1,371 million kilometres). Nevertheless, Saturn’s globe still exceeds 18 arcseconds in diameter, so a telescope magnifying just 100x will make it appear the same size as the Moon to the naked eye. The magnificent ring system is tilted 24 degrees toward us and spans 42 arcseconds tip to tip. Despite the low altitude, a 6-inch or larger telescope will deliver an image of Saturn that will remain etched in the memory when the seeing is good.
Saturn is easily identified since it is currently situated almost 13° (about the span of a fist at arm’s length) to the upper right of first-magnitude zodiacal star Antares in Scorpius for northern observers. But if you wish for an unequivocal celestial guide, then the the 11-day-old waxing gibbous Moon is just 2.2° to the upper right of Saturn in the south at 11 pm BST on 28 June as seen from the centre of the British Isles.
The Moon and Saturn will be close enough for the pair to be seen in the same field of view of telescopes and binoculars magnifying 20x or less, but their apparent proximity is of course a line of sight effect — the Moon is about 240,350 miles (386,800 kilometres) away from the UK on the night of 28 June, so Saturn is at least 3,500 times further away!
Saturn’s largest and brightest moon, Titan, may be found four ring diameters west of the planet (that’s to the left of Saturn in Newtonian reflectors and refractors/catadioptrics with a star diagonal) on the night of 2 July. Titan may be found a similar distance east of the planet on 10 July. Clear skies!
Inside the magazine
You can find out more about observing Saturn in the June edition of Astronomy Now in addition to a full observing guide to the night sky.
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