The splendour of the night sky in Africa has to be seen to be believed. Nothing in the Northern hemisphere quite prepares you for it. The dry, clear air, the absence of light pollution and the altitude of the high savannah grasslands all combine to open a window onto a universe one hardly knew was there. Especially in the southern half of the continent, where the tilt of the earth gives a direct view into the heart of the galaxy, the result is breathtaking. On any moonless night, the whole sky is a mass of light, from horizon to horizon. Straddling it, crammed with stars, trails the huge swathe of the Milky Way.

Nor is it just the scale of the experience that so impresses itself upon you. An extraordinary degree of detail can be observed, especially through binoculars. Where a single star winked in a void, dozens suddenly cluster. To lie on your back on a kopje in Zimbabwe, Botswana or the Karoo, is to gaze up into the remotest depths of space and time, and to experience those depths as a pulsating presence.

Why the astonishing difference? It is largely due to the Milky Way, with its awesome band of pale light. Passing the Southern Cross, it sweeps across the entire sky, an effervescence of thousands of stars. Its hidden shape is that of a vast disc with spiral arms, swirling around a suspected Black Hole in the centre - a sort of cosmic Catherine Wheel. Our own solar system lies on part of the Orion arm, about two-thirds of the way out from the centre. The Earth's tilt means that only a disappointing edge of the Milky Way can be seen from the Northern hemisphere. From the South, however, you can gaze through the teeming mass of stars towards the very centre.

When planning your trip, it is well worth taking note of the phases of the lunar cycle, and trying to ensure that your time in the bush will at least partly coincide with the darker nights associated with the new or waning moon. An African full moon is a phenomenon in its own right, as it rises impossibly huge and bloodshot over a dusty plain, or sheds its eerie light on water or vegetation. But compared to the full extravaganza of the Milky Way on a pitch-black night, it is a side-show.

If there is no moon, your eyes will quickly adjust to the darkness, and you will be able to see your way around by the light of the stars. These of course appear whitish only because the colour-registering cells in our eyes lack sensitivity at low light levels. In reality, as good binoculars will instantly reveal, they are a wash of ambers, pinks, blues or violets. Their twinkle arises from the light moving through alternating warmer and cooler temperature layers in the atmosphere.

If you can, try to bring with you some basic information about the night sky and its features. This is one area where your tour guide will probably not be of much help. Seek out and buy a southern Planisphere - a flat plastic map of the sky that rotates to provide correct location and time of month and day. You will also need a torch by which to read as you hold it aloft and try to piece the scene together. Or, you might begin with the map to the right.

First, rotate the page until the month of your visit appears at the bottom. The stars nearest to the month label will be in the North around 9pm. Those on the left will be in the West, and those on the right, East. About two-thirds of the stars displayed should actually be visible; the rest (nearest the top) will be hidden below the southern horizon.

The Southern Cross is a moving and powerful symbol, capable of bringing tears to the eyes of a traveller returning home. One of the easiest constellations to identify, it can be seen from as far north as Kenya. Its stars are arranged in a clear cross shape, with a fifth, rather fainter, to one side. Two bright stars further east in Centaurus point towards it. To find due South, you simply follow the line running down the cross to where it intersects an imaginary line that bisects the "Pointers". This is the position of the South Celestial Pole. There is no star here, unlike in the North where the pole star Polaris lies in the equivalent position. (Gazing up from the poles you would see the heavens draw huge circles of bright light as the Earth turns.)

While in this area, look out for the "Coalsack", a dark patch next to the brightest star at the bottom of the Cross. This vast blur of cool dust and gas visibly blocks the light of the Milky Way.

Two other exciting regions to be identified are the Magellanic clouds, named after the great explorer who noticed them in about 1520. They are best seen in the southern summer, appearing as bits broken off the Milky Way further south than the Southern Cross. They are smaller galaxies, relatively close by, which can be seen with remarkable detail through binoculars. The Large Magellanic Cloud is the more spectacular, with a bar across the middle and nebulae visible, including the great Tarantula Nebula.

Also easy to find is Orion, strangely upside down to visitors from the North. He is the mythological Hunter holding a curved shield of faint stars. The "Red Giant" located in the shoulders is Betelgeuse. It is old, its fuel nearly used up, so that it has cooled and vastly expanded. Soon (in astronomical terms) it will explode, becoming a supernova and sending out clouds of gas and dust. (Our Sun and the Earth originated from an event like this.) Diagonally opposite it lies Rigel, young, hot and very bright with a faint blue tinge. Below the three distinctively glittering stars in the belt, in amongst the "sword", is a fuzzy patch in which new stars are still being formed. This is the Orion nebula, probably the most beautiful of all the many stunning gas clouds to be seen.

In ideal black-night conditions, there is much else to beguile the eye. Shooting stars regularly blaze their fading trails across these skies. Military and civilian satellites cruise at high altitudes, betrayed by the flickering steadiness of their motion as they traverse the whole scene in just a few minutes. Any stray planets that have chosen the time of your visit to approach the Earth will hang so apparently low above your head that the instinct is to reach up and touch them. Venus is usually the brightest, Mars is slightly red and Saturn looks orange and cigar-shaped because of its rings. Planets change position slightly night after night, whereas stars in distant constellations appear fixed.

However, a word of caution. If your chosen kopje for transgalactic gazings happens to lie in Zimbabwe's Matobo Hills, the steadily winking green and red light that nearly stops your heart could turn out to be merely one of the regular London-Johannesburg flights!

To the Shona people, the Milky Way is gwara renzhou: "the path of the elephants". This all-night safari comes entirely free, and could prove as memorable as any on offer by day.

Star charts:

Planispheres are published by George Philip Ltd, an imprint of Reed Books, Michelin House, 81 Fulham Road, London SW3 6RB. ISBN: 0-540-01239-4. The Planisphere (pictured) is actually calculated for latitude 35 ° South (approximately Cape Town). However, it will still be useful slightly further north and can be used throughout the year, at any time of day.

More specific, customised charts can be created via the Mount Wilson website: www.mtwilson.edu/Services/StarMap/. Enter the latitude, longitude, date and time of day of your proposed star-gaze (anywhere in the world) and hope that the weather is all right on the night!

Published in Travel Africa Edition Fifteen: Spring 2001 Text is subject to Worldwide Copyright (c)