Science: Ten out of ten for star quality: Things are looking up for stargazers thanks to a new imaging system, says Bernadine Coverley

Amateur astronomers still look at the stars in spite of the glow that suffuses the night sky almost everywhere in Britain. Bright city lights have banished true darkness, making the faint, fuzzy galaxies difficult to distinguish through a telescope. But the celestial view from backyard observatories has been revolutionised by an electronic imaging system known the charge-coupled device (CCD).

Now even city stargazers can explore what they formerly knew only in theory and examine what they find at their leisure. The most distant galaxies appear on a computer screen using a CCD camera connected to a moderately powerful telescope.

'The universe is so much bigger with this gadget because it can penetrate more,' said Maurice Gavin, as he retrieved a stored image, a fragment from 'deep sky', and brought it up on screen. 'I can see stars that only professionals could see before, and I can get far superior images to those you can see through a telescope alone, even when the weather is bad.'

Mr Gavin is one of several hundred amateurs in this country who enjoy the advantages opened up by the use of CCD. As well as imaging faint and distant objects, it provides automatic steering by locking on to a star, and those with an interest in spectroscopy can explore what stars are made of and in which direction they are moving.

The lightweight head can be attached to the telescope or fitted inside the telescope tube riding piggyback on another. The interface links them with computer, screen and printer. The clarity of the images means that they can be photographed directly from the screen.

The British company FDE developed a prototype version of the CCD in 1990; since then quality has improved and prices have fallen; a starter system now costs pounds 370. Now CCD systems are exported as far as Japan.

Top of the range is a system called Starlight Xpress, which was launched last autumn and has its own minicomputer, high-resolution screen and low- noise cooling system for the longer exposures possible with a CCD camera. As its name indicates, it takes seconds to download the image of the galaxy or selected stars, and if there is anything of significance that small area can be enhanced and enlarged.

As Mr Gavin explains: 'Only a few seconds' exposure with CCD will record more stars in a globular cluster than are visible to the eye with the same telescope.' It reveals not only more detail but stars too faint to be seen through the amateur's telescope, such as Van Biesbroek's star, an 18th- magnitude red dwarf (the higher the magnitude the fainter the object).

If the idea of magnifying distant stars on screen destroys a certain magical charm associated with peering through a telescope in the cold, dark night, the benefits for astronomers are practical, as the CCD system overcomes such problems as the vagaries of the English weather and light pollution. Work in the observatory can be followed up on a better-quality PC in indoor comfort.

The CCD brings more complex detail from deep sky within observable range. Several separate exposures of the same object can be added together to produce clear images and thus avoid the fogging of longer exposures. The stored images do not deteriorate like photographic prints, and new images can be compared to see if anything has changed.

After all, serious amateurs are competitive. Asteroids and supernovas are the most likely potential discoveries and those who want to see their names in lights can send data to the Supernova Patrol. Images are jealously guarded. 'You tend to believe what's on your screen belongs to you,' said Maurice Gavin. 'I never send a disk to anyone before I have had time to examine every detail. You can't exactly copyright observations.'

CCD increases the possibility of discovering something, but it isn't a prerequisite. After all, Tycho's star is the remnant of a supernova observed by the Danish astronomer Tycho Brahe in 1572, before the invention of telescopes.

Of the 200 or so amateur astronomers using CCD in Britain, perhaps only half a dozen use the technology to analyse starlight. Placing a prism in front of the telescope stretches a point of light into a rectangle which can be interpreted for chemical composition through colours and for data on the star's movements.

The most favourable condition for observing is a clear, dark sky. Since the eye is incapable of detecting the colours without help, astrophotography has always been important. One of the delights of star gazing is capturing the images on film, whether it is the subtle colours of real space, pale pinks and blues, or the garish, false colours used to show detail.

Peak interest in astronomy as measured by membership of the British Astronomical Association was greatest at the time of the Apollo flights, yet all the techniques Nasa deployed then are now generally available. For those who still enjoy looking at the solar system and beyond, computing can bring out detail that was never visible before.

Professional astronomers at a recent conference were left gaping at images of the other side of the universe when they were shown astounding views from the space telescope Hubble 2. And as the professionals move into cosmology with the excitement of mapping the outer reaches of the universe, they leave the amateurs plenty of space closer to home.

(Photograph omitted)