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Chapter 1
Power Telescopes

Boldly Into The New Millenium

There is no better way to sample the state of the art of telescope-building—nor the promise of what is to come—than by attending an international telescope symposium, and that is where we start our story. Such events are not everyday occurrences, but the year 2000 saw a gathering of such significance that its deliberations will reverberate long and loud through the annals of astronomy. It was a very large meeting, embracing no less than thirteen separate conferences. It attracted 1,300 scientists, engineers, directors of institutions and household-name professors, all with a common interest in the tools of the astronomer's trade. In that broad forum, the mysteries of the Universe met the nuts and bolts of engineering, and in the willing hands of its participants lay the future of the telescope.

The symposium's title brashly declared its spirit: 'Power Telescopes and Instrumentation into the New Millennium'. It took place in Munich, during the last week in March—although the message that this was supposed to be springtime obviously hadn't got through. By turns, the participants endured icy winds, rain, sleet and snow on their daily journey to the symposium sessions. Only on the last day did the Sun finally put in an appearance.

In some ways, the symposium inside Munich's International Congress Centre was as tumultuous as the weather outside—although its cut and thrust were veiled in the subdued tones of academia. Let us join the participants, and eavesdrop on their deliberations. But, before we do, we should explore their passions a little further.



First, there was chauvinism. A rare species of chauvinism, to be sure—but that's what it was. It concerned the different varieties of telescope astronomers use today.

Until 1932, when Karl Jansky of the Bell Telephone Laboratories discovered radio waves coming from space, there was only one kind of telescope. It collected and focused ordinary visible light. It used the science of optics to allow information to be retrieved—at first by human eyes, and then, from the 1880s, by photographic plates.

Today, there are as many different kinds of telescope as there are varieties of natural radiation traversing the Universe. A plethora of names identifies these ghostly emissions—gamma rays, X-rays, ultraviolet rays, visible light, infra-red, millimetre waves (microwaves) and radio waves. Arranged in order of wavelength, they form the electromagnetic spectrum. Somewhere near the middle is the radiation to which our eyes are sensitive. Its wavelength is measured in nanometres (millionths of a millimetre), and ranges from about 400 nanometres (nm) for violet light to about 700 nm for deep red. In between lies the rainbow of the visible spectrum.

One of the heartwarming facts astronomers have brought to us in recent years is that the Earth is constantly bathed in radiation covering the whole electromagnetic spectrum. It comes from sources everywhere in the Universe. Much of it never reaches the surface of the planet because it is absorbed by the atmosphere. If you want to observe X-rays or gamma rays, for example, you have to mount specialised telescopes on spacecraft. But for some categories of radio and infra-red radiation—and visible light, too, of course—the observations can be made from the ground.

To distinguish them from their more exotic cousins, telescopes that use visible light are now called optical telescopes. They require darkness to operate, so observing with them is always night work. They also require clear skies. And, despite the effectiveness of the glamorous new flavours of astronomy, optical telescopes still play a vital role in the study of the Universe. It is the central position of visible light in the electromagnetic spectrum—and the fact that ordinary stars emit most of their energy as visible light—that keeps them in such high demand.

From Stargazer by Fred Watson, pages viii - x of the Prologue, and pages 1-17 of Chapter 1. Copyright Fred Watson. All rights reserved. Excerpt reproduced by permission of Da Capo Press.