See ringed planet Saturn at its best in July 2019

By Ade Ashford

30 June 2019 Ade Ashford

This looping animation shows the southern horizon as seen from the British Isles on consecutive sidereal days around 12am BST from 14 to 17 July 2019. Hence the stars appear stationary and the motion of the Moon, Jupiter and Saturn is more easily perceived. For scale, the view is about 50 degrees wide, or a little more than twice the span of an outstretched hand at arm’s length. Note: the Moon’s apparent size is enlarged three times for clarity. AN graphic: Ade Ashford.
As July opens, any observer in Western Europe with a clear sky around local midnight cannot fail to notice the conspicuous ‘star’ that is Jupiter low in the south. If you’re still up around 1am, take a look about a span-and-a-half of an outstretched hand at arm’s length to Jupiter’s left and, at a similar height above the horizon you’ll find another giant of the solar system – Saturn. By mid-July, Saturn and Jupiter straddle the southern meridian at local midnight, as depicted in the animation above.

Shining at magnitude +0.1, Saturn is twelve times fainter than its larger planetary sibling to the right, but the ringed planet is still brighter than anything else in the constellation of Sagittarius in which it presently resides. In common with Jupiter, Saturn currently occupies a region of the ecliptic that struggles to attain a peak altitude of 14 degrees in the south for observers in the heart of the UK, but it’s still worthy of a look through any sized telescope.

A computer simulation of Saturn’s appearance at 20:37 UT (9:37pm BST) on Tuesday, 9 July 2019 – the planet’s opposition day and the instant that it’s closest to Earth for 2019 at a distance of 9.03 astronomical units (1,351 million kilometres). Saturn is best viewed from the UK around 1am in early July, found barely a span-and-a-half of a fist at arm’s length above the southern horizon. However, even at such a low altitude, on nights of steady seeing the planet’s glorious rings – with the planet’s north pole currently tilted by 24 degrees towards our line of sight – are glorious to behold in any telescope. What’s the smallest telescope in which you can perceive the Cassini Division, the thin black line between the planet’s A & B rings? AN graphic by Ade Ashford/Stellarium.
Observing Saturn
With a declination of -22 degrees, Saturn is currently best seen from the Southern Hemisphere. As viewed from Australia, for example, the ringed planet is virtually overhead when on the meridian. Saturn’s low altitude from the British Isles means that getting clear views will be challenging in July 2019, but there are ways that you can improve your chances.

Always give your telescope ample time to cool down to nighttime temperatures by uncapping the lens or mirror (with the tube horizontal to avoid dew settling on the optics) an hour before making observations. Also, observe from a grassy location wherever possible, avoiding concrete or asphalt that retains heat after dark. And don’t view Saturn over rooftops where turbulent warm air currents rise.

Try to view Saturn within an hour or so of the time it transits (see our interactive Almanac for local times) so that it’s as high as possible above your horizon. Calm, slightly misty nights when a high-pressure system sits above us often provide the steadiest planetary views.

However, even in fine UK seeing, both Jupiter and Saturn will display atmospheric dispersion (where the upper and lower limbs of the planet may appear to have prismatic blue and red fringing, respectively) due to our atmosphere acting like a weak lens. You can buy atmospheric dispersion filters to help counteract this, or simply use a yellow/orange filter to lessen the coloured fringes.

The aspect of Saturn and the orbits of its brightest moons Titan and Rhea around opposition in July 2019. Observers with Newtonian/Dobsonian telescopes should rotate this image through 180° to match their eyepiece view, while users of refractors and catadioptrics (Schmidt- and Maksutov-Cassegrains) with a star diagonal need to mirror this graphic left-right to replicate what they see through the eyepiece. AN graphic: Ade Ashford.
Saturn’s bright moons
The largest Saturnian moon, 3,200-wile-wide Titan, orbits its parent planet every 16 days and is easy to spot in telescopes of 5-cm (2-inch) aperture or larger as it shines at magnitude +8.5. Titan is at elongation, 4¼ ring diameters east of Saturn, on 3 and 19 July. Titan can be found the same distance west of the planet on 11 and 27 July.

Saturn’s second-largest moon Rhea with a 4½-day orbit is also easy to spot at magnitude +10. Elongations two ring diameters east of Saturn occur on 2, 11, 20 and 29 July. Rhea can be seen the same distance west of Saturn on 4, 13, 22 and 31 July.

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