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As George said: “Totally obscured!” Chapter 35 Four Hundred Years of the Telescope Allan Chapman and myself on 15 February 2008 Credit: Patrick Moore... It was far better than any of Gal

P Moore, The Sky at Night, DOI 10.1007/978-1-4419-6409-0_35,

© Springer Science+Business Media, LLC 2010

For the first week of the New Year, several programmes on BBC2 were to commemorate the 400th anniversary of the first astronomical observations made with telescopes The first of these programmes was the “Sky at Night” We decided to look back at some

of the telescopes we had visited since that first programme, way back in 1957.

Various people were shown – in various locations – and we used extracts from the actual interviews The earliest, I think, was with George Hole, for the 50th programme We were down at Brighton, with George’s fine 24-in reflector, hoping

to give direct views of Jupiter and Saturn Of course, it was “live” – everything was, in those days – so that we were at the mercy of the clouds Five minutes before transmission, and 5 min late, the sky was brilliantly clear, but during the actual transmission cloud-cover was complete As George said: “Totally obscured!”

Chapter 35

Four Hundred Years of the Telescope

Allan Chapman and myself on 15 February 2008 (Credit: Patrick Moore)

138 35 Four Hundred Years of the Telescope

I introduced the programme from my observatory at Selsey Among astronomers shown were Allan Chapman, Howard Bond, Kim Hermann, Peter Wehringer, Roger Angel, Pete Lawrence, Michael Barstow, Jeff Hoffman, Geoff Marcy, John Culshaw, Michelle Dougherty, Richard Ellis, and of course, Chris Lintott Quite a galaxy – but it was a pity about those clouds…

Who invented the telescope – and who first turned a telescope skyward? Most people would say “Galileo”, but they would be wrong The first telescope about which we have definite information was made by a Dutchman, Lippershey, in

1608 Earlier reports coming from England are interesting, but not conclusive Unfortunately for himself, Lippershey did not take prompt steps to establish priority, and other telescopes quickly appeared over Europe Galileo obtained one during 1609, and “sparing neither trouble nor expanse”, as he put it, made one for himself

On July 26, 1609, came the first known astronomical observation made with a telescope; Thomas Harriot, one-time tutor to Sir Walter Raleigh, used his tiny

“Dutch tube” to look at the crescent Moon and to marvel at the mountains, the valley, the craters, and the grey plains we still miss-call “seas” Within a year or two, he had constructed a remarkably good map of the Moon It was far better than any of Galileo’s lunar work, but he did little else astronomically, and it is Galileo who is rightly called the first true telescope observer From January 1610, he made a series

of spectacular discoveries, notably the four main satellites of Jupiter, the phases of Venus, spots on the Sun, and the “myriad stars” of the Milky Way He even saw that there was something strange about the appearance of Saturn, though he could not make out its true nature

Galileo’s most powerful telescope magnified a mere 30 times, and was nothing like so effective as a pair of modern binoculars, quite apart from the fact that it had inconveniently small field of view Its object-glass is convex, and the eyepiece lens

is concave; a “Galilean” is bound to give a great deal of false colour It was some time before this problem could be tackled, and although it is true to say that modern lenses give very little false colour, it would be wrong to claim that they give none

at all

Isaac Newton never did solve the problem, which was one reason why he aban-doned refractors altogether and turned his attention to reflectors, building the first

“Newtonian” 60 years after Galileo’s pioneering work This certainly eliminated false colour, and a mirror is much easier to make thank a lens, but of course they have their disadvantages too Reflectors can be temperamental, and requite regular servicing, which a refractor does not

For an early programme I did show Galileo’s telescope, and also Newton’s, but let me move on to the largest nineteenth century, the 72-in reflector at Birr Castle,

in Southern Ireland It was homemade by the third Earl of Rosse, who had a lively interest in astronomy and is the supreme example of what my old friend Dr Allan Chapman called a “grand amateur” Lord Rosse wanted to build a telescope larger than any of its predecessors (at that time the record holder was Sir William Herschel’s 49-in reflector) and, amazingly, he succeeded even though he had to

35 Four Hundred Years of the Telescope

make his own equipment and cast the huge metal mirror, an alloy of copper and tin – the casting process, vividly described by an onlooker, must have resembled a major display of pyrotechnics The only assistants came from the Earl’s, and were workers trained by Lord Rosse specially for the purpose

The telescope was unwieldy and difficult to handle but it worked well, and was used to show the spiral structures we now know to be galaxies It was, for some time, in a class of its own, but later in the century was overtaken by the new large refractors For many years, it was out of action, but thankfully is now fully opera-tional again (I am proud to say that I had something to do with this) It remains unique in the history of science

Refractors were in vogue near the end of Victorian times, and almost all the largest telescopes of this kind were built before 1900 – notably the largest of all, the 40-in at the Yerkes Observatory This may be the useful limit, because an object-glass has to be supported round its edge, and if too heavy will distort under its own weight A 49-in was once made, but was a total failure, so that for Earth-based telescopes, at any rate, the Yerkes 40-in is not likely to be surpassed I admit that my own favourite is the 24-in of the Lowell Observatory in Arizona, which

I used a great deal in my pre-Apollo Moon-mapping days

There is one branch of observational amateur for which a refractor is far more suited than a reflector: solar work Turn a Newtonian toward the Sun, and you are likely to cook your secondary Heat is bad for mirrors, and also for eyepieces Much the best way to study the solar surface is to use a refractor, and project the image

on to a screen fixed behind the eye-end of the telescope Moreover, adding H-alpha equipment is relatively easy with a refractor, the main problem being finance Come back now to our historical story After the large refractors we reach the twentieth century, and the dominance of single-mirrors Glass, coated with a thin layer of silver or copper, took over from metal, and progress was amazingly rapid, due largely to George Ellery Hale, in America Hale’s constant call was for “More light!” and he master-minded first a 60-in and then, in 1917, a 100 in both of which were set up on Mount Wilson in California Hale was well aware of choosing sites with the best available seeing conditions, and this meant high altitude, above the thickest part of the Earth’s atmosphere For three decades, the 100-in reflector was in a class of its own, “spiral nebulae”, measuring their distances and proving the spirals were separate galaxies, far beyond our Milky Way No other telescope

of the time had sufficient power to make observations as delicate as this

The 100-in remained the largest until 1948, with the completion of the 200-in

on Palomar Mountain (again planned by Hale, though sadly, he did not live to see

it finished) The 200-in was supreme for a while, and in 1952 enabled Walter Baade to show that the observable universe was twice as large as had been believed But two major developments lay ahead

The larger mirror, the more difficult it is to make Quite apart from this, these is the problem of our unsteady atmosphere By the end of the war virtually all astro-nomical research was carried out photographically, so that images were blurred New techniques, known as active optics and adaptive optics, reduced these effects very significantly But even more important was the rise of electronics, and well

140 35 Four Hundred Years of the Telescope

before the end of the twentieth century electronic devices had taken over from sensitive plates, just as photography had superseded visual observations a 100 years earlier

On my study wall, I have an image of Saturn taken with my 15-in reflector a few weeks ago It is far better than anything which could have been produced by the best professional observatory as recently as 1990 Electronic aids have made all the difference

The Palomar reflector is no longer the world’s largest, and is not even in the

“top twenty” Atop Mauna Kea in Hawaii, 14,000 ft above sea-level, you will find the Keck I and Keck II telescopes, each with a 100-m (387-in.) mirror and capable

of working together On Cerro Paranal, in the Atacama Desert of Northern Chile,

is the VLT or Very Large Telescope, where each of the four components has

an 8-m (630 in.) mirror Together, they can pick up the light of the objects over 13,000 million light-years away – and remember, the universe as we know it is no more than 13.7 thousand million years old These huge mirrors are not single, but segmented, i.e made up of hundreds of individual parts fitted together to form the correct optical curve

There are of course space telescopes orbiting the Earth, so that seeing condition are perfect all the time, and no incoming radiations are blocked out by the Earth’s atmosphere The 94-in Hubble Space Telescope, launched by NASA in 1990, was the first; others have followed and have provided data impossible to obtain from ground level

We have indeed come a long way since Harriot had that first view of the crescent Moon through his time “Dutch tube”, 400 years ago How far will we go during the next 400 years? Your guess is as good as mine!

P Moore, The Sky at Night, DOI 10.1007/978-1-4419-6409-0_36,

© Springer Science+Business Media, LLC 2010

Polar lights – Aurora Borealis in the northern hemisphere, Aurora Australis in the southern – have been known since early times; in Scotland, they were called the

“Merry Dancers”, supernatural beings enjoying themselves in the heavens To Eskimos, they represented a game of football played by spirits using a walrus-head

as a ball From England, they are not often seen really well; from higher latitudes, they are more frequent, and can be breathtakingly beautiful.

For this programme Chris Lintott and Pete Lawrence went to Tromso in North Norway, and were rewarded with a brilliant display Sadly, I could not go (I love Tromso), but back in Selsey I was joined by two researchers deeply involved in this work; Dr Chris David, from the team STEREO (Solar Terrestrial Relations Observatory) and Professor Tony van Aiken, former Director of EISCAT (European Incoherent Scatter Scientific Association), which uses three radar systems in

Chapter 36

The Merry Dancers

Aurora (Credit: Peter Lawrence)

142 36 The Merry Dancers

Scandinavia to study interactions between the Sun and the Earth as revealed by disturbances in the ionosphere and the magnetosphere.

I first saw the Northern Lights in 1938 – not from Norway, but from my then home time, East Grinstead in Sussex It was a beautifully clear winter evening and the whole sky was glowing a brilliant red I wondered whether there could be a huge fire somewhere in Ashdown Forest, and it took me several minutes to realise that I was being treated to a brilliant display of aurora After all, a Roman emperor, the much-maligned Tiberius, once made the same mistake when he sent his fire-fighters to quench what he thought was a huge blaze in the port of Ostia

After that display, I began to look up old stories and legends about the Lights

I found plenty of them The nickname “Merrie Dancers” is Scottish; supernatural beings were cavorting about in the heavens – not always peacefully, because a red aurora showed that blood had been spilt From Scotland aurorae are more frequent than they are south of the border To some of the Eskimos, an aurora indicated a game of football played by spirits using a walrus-head as a ball (perhaps Reykjavik United versus Longyearbyen Town?) but in Siberia the tables were turned, where the walruses were the players and the ball was the human head In Russia, the Lights were associated with the fire dragon Ognenniy Zmey, who approached women and seduced them while their husbands were away There are legends everywhere The Greenlanders believed that people who had passed on to the next stage of existence were signalling to their kinsfolk who were still on Earth The Faroe Islanders kept their offspring indoors during displays, in case the Lights came down

and singed their children’s hair, while in Estonia the aurorae were down virmalised,

spirits from higher planes, sometimes friendly and sometimes not To the Inuit of Alaska the Lights are people who have gone to the sky and are dancing to remind

their loved ones that they are still around The Finnish name for aurorae is revontulet,

or sparks whisked upward when the Lapland foxes wagged their tails The Sami people believed that the Lights (guovssahasat) could be dangerous, and might even descend and kill anyone who made fun of them And in parts of Scandinavia it was said that the Lights were warlike Valkyries, “mounted upon horses and armed with helmets and spears…When they ride forth…their armour sheds a strange flickering light, making what men call the “aurora borealis (Thomas Bullfinch, 1855)” There were more scientific explanations too In Denmark and Sweden, it was believed that aurorae were due to volcanoes in the far north, put there to provide mankind with light and heat The Inuit of Hudson’s Bay thought that the sky was a solid dome, and that the stars were holes letting through light from a shining background But my favourite explanation is Norwegian; the Northern Lights are reflections in the sky cast of swarms of presumably luminous herrings swimming happily in the Arctic Ocean!

Early astronomers had their own ideas The Greek philosopher Anaxgoras (c 500–428 bc) knew about aurorae, even though they are seldom seen from Greece, and attributed them to fiery vapour poured down in to the clouds above, while the Roman writer Se eca (5 bc–ad 65) put them down to currents of boiling

at very high altitudes Because the stars moved so quickly, they could emit enough

36 The Merry Dancers

heat to set them alight The term “aurora” was coined by the French astronomer

P Gassendi in 1621, and the first scientifically accurate account was written in

1650 by K Gesner of Zurich

It is not true that aurorae are the best seen from the North Pole – far from it The electrified particles from the Sun do make for the north magnetic pole, but are captured by the Earth’s magnetic field, and the most favourable observing site are

in the “auroral oval”, a belt centred on the magnetic pole Generally, the Oval remains north of England and brushes Scotland, but during a solar storm it may broaden sufficiently to cover the whole of the British Isles I have hunted aurorae

in Hudson’s Bay, Alaska, Finland and Norway, but I have had my best views from Tromso in North Norway, which is why I took “Sky at Night” viewers on trips there, though I admit that I was influenced by the fact

P Moore, The Sky at Night, DOI 10.1007/978-1-4419-6409-0_37,

© Springer Science+Business Media, LLC 2010

At the time of this programme, Saturn was in Leo at opposition and thus well place observation The rings were edgewise-on, so that the planet was temporarily shorn

of its beauty, but to make up for this, there was a great opportunity to watch the satellites Two were very much in the news: Enceladus With its icy fountains, and Titan, with its chemical lakes The Huygens space craft, still orbiting Saturn and

Chapter 37

The Fountains of Enceladus

Fountains of Enceladus (Credit: NASA)