TOURING THE SOLAR SYSTEM

From the Moon’s majesty to the wonders of the planets, the Solar System offers much to the vigilant astronomer

Wherever you live, each clear night presents an opportunity to observe a variety of objects and phenomena within the Solar System. Viewing the Solar System’s most prominent objects is far less hampered by the detrimental effects of light pollution than attempting to glimpse faint deepsky objects. Presenting such a large and bright target, the Moon’s varied marvels can be enjoyed from virtually anywhere through any optical aid, from binoculars to telescopes of any size. Within reach are hundreds of craters of different shapes and sizes, dozens of impressive mountain ranges, a smattering of vast grey plains and countless ridges and valleys.

A low magnification will take in the entire Moon, but if you want to view the lunar surface, or indeed discern detail on any of the planets, you’ll need to use a magnification of at least 100x. Under ideal conditions, your maximum practical magnification works out at about twice the diameter of your telescope’s aperture. High magnifications aren’t easy to employ if you have an undriven telescope, as the object will appear to move faster across the field of view the more magnification is used – 100x is about right. A driven telescope eliminates the need to manually track the object, allowing higher magnifications to be used more effectively. A Barlow lens is most useful for this: a 2x Barlow will double the magnification delivered by any eyepiece.

Mercury and Venus both circle the Sun within Earth’s orbit, and neither planet appears to stray very far from the Sun.

Both display a sequence of phases during each elongation from the Sun, as well as changes in their apparent diameter, all of which can be followed through a small telescope. Detail on Mercury’s surface is very subtle and requires good viewing conditions. This tiny planet whips round the Sun in a very tight orbit, meaning it’s one of the hardest planets to observe since it’s only visible just before or after sunset. Care must be taken when observing an object that so closely hugs our star to avoid damage to the eyes.

Venus is shrouded in a dense atmosphere, but occasional cloud detail can be made out on the planet’s dazzling disc. When it’s visible in the sky – be it early morning or in the evening – Venus is a prominent, brilliant object; you really can’t miss it, since it’s the brightest object in the sky after the Sun and Moon. The planet’s appearance changes as then nights pass, and you’ll see its changing phases as the bright planet circles the Sun.

Further out and beyond Earth orbit, Mars presents a fascinating object through any eyepiece, particularly when the planet is nearest Earth. The Red Planet’s surface shows a patchwork of bright, dusky desert tracts, plus brilliant white polar caps, while dust storms and clouds can occasionally be seen in Mars’ atmosphere under high magnification and good viewing conditions.

Jupiter, the Solar System’s giant planet, is fascinating to observe. The planet’s thick, gaseous atmosphere is always a tumult of activity – there’s always something going on in its parallel dusky belts and bright zones, from spots, storms and festoons – and you’ll see detail on its broad disc through virtually any telescope. Jupiter boasts four particularly bright moons, and their orbital dance about the planet can be followed even through binoculars as small points of light on either side of the planet’s disc.

Saturn is renowned for its gorgeous ring system. Sometimes the rings are wide open and easily discerned through virtually any telescope, presenting a sight that never fails to impress the telescopic viewer. Subtle belts and zones can be seen in the planet’s atmosphere, but activity is far less noticeable than on Jupiter. Distinct differences in brightness within the rings can be made out, along with a narrow division between the main rings that’s known as the Cassini Division. You’ll also notice the shadow of the rings on Saturn’s globe and the shadow of the globe on the far side of the rings.

Due to their immense distance from Earth, Uranus and Neptune are much harder to observe, even with powerful telescopes. However, their pale-green and blue hues give them away from background stars.