REDSHIFT 2, Maris Multimedia, Pounds 49.95, Macintosh/Windows dual platform

Right ahead of you is the biggest planet in the solar system. Multi-hued Jupiter, with its entourage of swiftly-circling moons, is now centre stage. By the second, it is growing. As its south pole looms ever larger, you realise there is no turning back. For you are Comet Shoemaker-Levy 9, on a fateful collision course with the king of the planets.

Or you have just blasted off from Cape Canaveral. Earth shrinks rapidly into a pretty blue bauble, suspended in the black immensity of space. It takes an age to cross the blackness. But finally, your destination hoves into sight: Earth's battered and barren moon. You swing around its far side, passing dangerously close to its cratered surface. This time you are on board Apollo 13 and praying for a safe return home.

Redshift 2 is truly staggering in the amount of information you can extract from it. The first version of Redshift quickly attained the reputation of the best astronomy CD-Rom around, largely on the grounds that it passed the basic thresholds that 90 per cent of CD-Roms fail. It contained far more information than could be packed on a set of floppy disks, and it was truly interactive (unlike the many releases that could be equally well presented as a video with footnotes).

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Redshift 2 contains information on 250,000 stars, and 40,000 "deep sky objects" - nebulae, star clusters and galaxies - drawn from a plethora of catalogues, many of them fairly esoteric even for the professional astronomer. And the CD-Rom can plot the positions of more than 100 comets and 5,000 asteroids - as well as the Sun, Moon and planets.

You can view these objects from any location in the solar system you like, at any time - and in a fraction of a second. For those of us who remember plodding through orbital calculations and spherical trigonometry on a hand calculator, this still seems like magic. Maris has triumphed in building some immensely powerful computing engines into this software.

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As well as all this power to the aficionado's elbow, Maris has put some careful thought into introducing astronomy to the beginner. Tutorials run preprogrammed sequences to show anything from the Earth's seasons to a circuit of Saturn and its inner moons as seen from its outer satellite Iapetus. And new in Redshift 2 is a set of ten "guided tours". Turn to these mini-videos to investigate more abstruse astronomical topics, from the workings of the Big Bang to the mechanism of a nova explosion. Despite an irritating voice-over, the guided tours are refreshingly accurate and up to date.

The meat of Redshift 2 is in the main program. The "planetarium" part gives you a view of the sky from wherever you want. You can choose to look from any part of Earth's surface, and there is a useful map to help you find your location (which seems to default to Aachen). If you want to skywatch from a pukka professional observatory, the program lists scores - including the innumerable outstations of the Beijing Observatory. And if you tire of Earth, then you can gaze at the heavens from any planet in the solar system (and even from the surface of the Sun).

The planetarium has a zoom control that lets you look as deep into the sky as you want. It also lets you select which kinds of objects you want to see, and how faint you want them to be. It is quite an experience seeing thousands of asteroids zipping across the screen, like a swarm of fireflies. And if you want to play time traveller, there is nothing to stop you going back 15,000 years to see how the sky looked then. Or if you want, you can call on the "conjunctions" part of the program to tell you about the Jupiter-Saturn conjunctions in 7BC - the best bet for the Star of Bethlehem. If eclipses are more your thing, they are all there, too.

But there is a price to pay for all this sophistication. Because the team has gleaned its data from the most advanced catalogues and databases available, some very obvious skysights have slipped through the net. For instance, the Orion Nebula is not marked, or even graced with its most common catalogue number, M42. The two most striking sights of the southern sky - our satellite galaxies, the Magellanic Clouds - are not shown either (presumably because they are not in any catalogue). Two bright galaxies of the northern skies, Andromeda and the Triangulum galaxy M33, are marked - but not identified with their common catalogue numbers (and to add to the confusion, the quiet little spiral M33 is classified as a radio galaxy).

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Redshift 2 is fine if you want to get information on an obscure X-ray source. But beginners will be disappointed if they cannot identify some of the more obvious skysights. We understand that Maris Multimedia is aware of these shortcomings (partly caused by the rush to hit the Christmas market), and that future pressings of the disc will be corrected.

Detailed maps cover the major features on the Earth, Moon, Mars and Venus - and you can use these maps interactively to choose a location for viewing the sky. The CD-Rom includes a strangely patchy selection of video clips: you can view the Moon, Venus, the active galaxy M87 and two galaxies tearing stars out of each other, but not well-known Nasa videos of Mars, Jupiter and Saturn - let alone any videos of the Earth from space. A "photo library" contains 700 eye-catching and up to date images - though, once more, patchy rather than comprehensive. Again, speed of compilation seems to have worked against a uniform selection.

Also available is the complete text of the Penguin Dictionary of Astronomy by Jacqueline Mitton, which - in hard copy - is the standard astronomy dictionary on our bookshelves. Maris has beaten the printed word hollow with the delight of hypertext links and also links to the photo library.

It is fitting that a work of such cosmic vision has been compiled by an international team. The music ("The Redshift Suite"), was specially composed by the French musician Jean-Pierre Garatoni. The task of delivering the product was masterminded by Nick Maris, of Greek ancestry. And the CD-Rom itself was compiled by an 85-strong team of Russians - all former engineers and scientists, victims of cuts in the space programme. The dedication - "Maris Multimedia respectfully dedicate RedShift 2 to the brave men and women of the Russian space programme" - could not be more appropriate.

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Heather Couper and Nigel Henbest researched astronomy at Oxford and Cambridge respectively, and run Pioneer Productions - a TV company specialising in factual programming.