11 September 2024

See Saturn close to the Moon on the evening of 26 July

By Ade Ashford

26 July 2015 Ade Ashford

In the dusk twilight of Sunday, 26 July, around 10:30pm BST from the centre of the British Isles, ringed planet Saturn and the waxing gibbous 10-day-old Moon will lie just seven degrees apart. This graphic depicts the south-southwest horizon in a view that is 45 degrees wide, or twice the span of an outstretched hand at arm’s length for scale. Antares, the first-magnitude zodiacal star that is the brightest in the constellation Scorpius, lies ten degrees (about the span of a fist at arm’s length) to the lower left of the Moon this night. AN graphic by Ade Ashford.

In the last days of July, Saturn may be glimpsed low to the south-southwest horizon in the dusk twilight from the British Isles — a sign that the ringed planet’s summer apparition is drawing to a close. Saturn’s distance from Earth has increased somewhat from opposition on 23 May. The gulf between our two worlds now stands at 9.52 astronomical units (AU), or 885 million miles (1,424 million kilometres).

Nevertheless, the diameter of Saturn’s globe still spans 17.5 arcseconds, so a telescope magnifying just 100x will make it appear the same size as the Moon to the naked eye. The magnificent ring system also spans 40 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.

Unless you have an equatorial or GoTo telescope mount, finding Saturn in twilight can be a challenge, but an unequivocal celestial guide in the form of a 10-day-old waxing gibbous Moon lies just 7° to the upper left of Saturn in the south-southwest at 10:30 pm BST on 26 July 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 binoculars magnifying 7x or less, but their apparent proximity is of course a line of sight effect — the Moon is about 239,900 miles (386,100 kilometres) away from the UK on the night of 26 July, so Saturn is almost 3,700 times further away.

Saturn’s largest and brightest moon, Titan, may be found four ring diameters east of the planet (that’s to the right of Saturn in Newtonian reflectors and refractors/catadioptrics with a star diagonal) tonight. Titan may be found a similar distance west of the planet on 2—3 August. Clear skies!