For an eye on the sky, as Comet Hale-Bopp fast approaches, binoculars are your best bet,
"Comets are like cats,," said the astronomer David Levy. "They have tails, and they do precisely what they want." He could have added that people are fascinated by them, too, as the interest in the latest comet to come our way shows. Comet Hale-Bopp is visible already, and will be at its brightest in the northern hemisphere in late March and early April when it's a mere 120 million miles from Earth. As this is the closest it gets during its orbit of some 3,000 years, is it the time to rush out and buy a telescope?

"Absolutely not," says David Lawrence, the Technical Manager of Broadhurst, Clarkson and Fuller Ltd in London's Farringdon Road, which has been selling telescopes since 1785. "Most people think that because it's a comet you must buy a telescope to get a good look, and they go into Argos or Dixon's and buy the cheapest they can get. In fact it's very rare to use a normal telescope to look at a comet like Hale-Bopp, because a comet is quite a large item in the sky. A telescope will show you just a very small part of it. You might see the fuzzy nucleus but you would miss the tail."

Lawrence's advice is to buy a good pair of binoculars instead, which, after all, are merely two small telescopes that can be focused simultaneously. He recommends the Russian-made Hellos brand, starting at about pounds 50. "You want a pair that's about 7x50 or 10x50 at the most. They're also dual- purpose in that you could use them for bird-watching or take them on holiday."

The first figure represents the magnification power of the lens, and the second the size in millimetres of the objective lens - the big end. If you choose a magnification power bigger than about 10, the binoculars become too heavy to hold steady without a tripod. The wider the objective lens, the wider the field of view and the better the image, as more light is available. However, there is obviously a practical limit on how big a view you can see, and how many times you can magnify it, before you end up with binoculars the size of two milk bottles. Compact binoculars often have an objective lens that's only 20-25mm across, making them light to carry but limited on the detail you'll get.

"The next price level up from the pounds 50 Helios ones," says Lawrence, "is about pounds 100. At that level we'd recommend names like Halina and Pentax, or a range we stock called Viking. To be honest, there are very few manufacturers and binoculars from the same factories just go out under different brand names. You have to virtually double the price each time to get a noticeable increase in quality, so the next level up is about pounds 200. A pair for pounds 140 is not that much better than a pair for pounds 100, but if you're prepared to spend pounds 200 then you will see an improvement. The best advice you can give is for people to choose whether they want to spend pounds 50, pounds 100 or pounds 200, and then just find a pair they like. But for a beginner, spend pounds 50 on Helios and you'll get a perfectly good pair of binoculars."

When a salesman tells you not to spend money, you feel like you must be looking at the world through the wrong end of a pair of binoculars, but his advice is echoed by Ken Sheldon, who edits the newsletter of the Federation of Astronomical Societies. "More people are put off astronomy by getting a cheap telescope. Unless it's a good make you won't see things clearly, they won't be sharp and you'll be disappointed. Get a decent pair of binoculars to get a good look at Hale-Bopp. My own are an old pair made by the East German Zeiss company, which cost about pounds 100 and are quite brilliant."

In good weather conditions Hale-Bopp is already visible to the naked eye, as Ken Sheldon confirms. "I saw it only yesterday morning. I got up at 5am and the sky was nice and clear so it was easy to see with the naked eye, at about 15-20 degrees up from the horizon. It's as bright as any star but it doesn't have a huge tail, though even with the naked eye you can see that it is quite clearly not a star. I had another look three or four days ago when it was a little bit misty and then I did need binoculars. But if it does materialise in the way that it promises then it could develop into something quite spectacular."

The federation has about 3,800 members, and interest in astronomy is such that Ken's wife Chris, who is the secretary, receives two to three inquiries every day from people looking for their nearest group. When the BBC broadcast a radio series about astronomy a few years ago, 300 letters arrived in the first month.

David Lawrence confirms the upsurge in interest when a comet like Hale- Bopp grabs the attention. "When something like this makes the national newspapers we notice the additional customers. If there's an item on the TV news, you can guarantee we'll be much busier the next day."

Broadhurst Clarkson and Fuller has been selling telescopes since they began to become widely available in the late 18th century. Their invention is generally credited to a Dutch optician, Hans Lippershey, in 1608, and opticians continued to play a big role. John Dollond invented the achromatic object glass in 1757, which enabled better refracting telescopes to be manufactured.

"The Farringdon-Holborn area was the optical-producing area of London," says David Lawrence, "and one of the first opticians to make a telescope, Charles Tulley, was based on this site."

Tulley would no doubt be astonished to see the huge brass telescope that fills the shop window, a model from 1860 that's worth about pounds 20,000. That's also the price for the top-of-the-range modern computerised telescopes, for sale to universities and well-to-do amateur astronomers.

"If something like Hale-Bopp does excite people's interest," Lawrence says, "then from a buying point of view the choice is fairly straightforward. If you want to get a telescope for looking at the stars and planets then you will have to spend about pounds 250. There's a good choice at that price level, but beyond that there's nothing until you get to the pounds 650-pounds 700 price range. Then you'll get something with an electric drive which will allow you to do photography, where of course stability is all-important. Between those two price levels there's nothing."

More difficult might be finding somewhere to buy, as the shop in Farringdon Road is the only one of its type in Britain. "The nearest shop like ours," says Lawrence, "is in Paris, and there are two more in Germany. There are some other people in other parts of the country but they are mostly working from home and making telescopes to order rather than to sell direct to the beginner. David Hinds in Tring distributes and makes telescopes, and there's Beacon Hill Telescopes in Humberside, but they only make stuff to order. The best advice I can give people outside London - if they don't want to ring us up or use the mail-order service - is to go to their nearest bird-watching specialist and get a good pair of binoculars."

And if you have pounds 20,000 to spare, the brass model in the window is for sale, but only when they find a replacement. "That's about the fourth one we've had. People from Disney are interested in it. We sold the last one to the Sultan of Oman."

Broadhurst, Clarkson and Fuller, 63 Farringdon Road, London EC1 (0171- 405 2156). The Federation of Astronomical Societies, Whitehaven, Maytree Road, Lower Moor, Pershore, Worcs WR10 2NY. British Astronomical Society (0171-734 4145).

David Hinds, distributor and manufacturer (01442 827768). Beacon Hill Telescopes, manufacturers (01472-692959).

Aviatours is running flights from Heathrow and Manchester to view Hale- Bopp from 37,000ft on 29 March at a cost of pounds 125 (01252 793250 or 0161- 832 7972).