The Skywatcher’s Handbook - Night and Day. What to Look for in the Heavens Above

226 Pages·1985·61.09 MB·English

by  Colin A. Ronan

§ ШШШЖ
THE SKYWATCHER’S
H AN D BO O K
NIGHT AND DAY
WHATTO LOOK FOR IN THE HEAVENS ABOVE
CONSULTANT EDITOR
COLIN A. RON AN MScFRAS
0
CORGI BOOKS
THE SKYWATCHER’S HANDBOOK Colin A. Ronan, MSc FRAS is the
editor of the Journal of the British
Conceived, edited and designed
Astronomical Association and was
by Marshall Editions Limited
recently a member of the Council of The
71 Eccleston Square, London SW1V 1PJ
Royal Astronomical Society. As well as
being a trained astronomer and historian
A CORGI BOOK
of science, he has found time to write
ISBN 0 552 99146 5 (softcover)
0 552 99196 1 (hardcover) more than 25 books - one of which (a
biography of Edmond Halley) has become
First publication in Great Britain a standard work. At present he is
Corgi edition published 1985 working on a multi-volume abridgement
Compilations, design and text of Joseph Needham’s Science and
The Night Sky (by Colin Ronan) Civilization in China, being published by
© 1985 Marshall Editions Ltd, Cambridge University Press.
London SW1V 1PJ, England
The Daylight Sky
© 1985 Storm Dunlop Storm Dunlop, FRAS FRMetS is
Observing and Recording the Sky currently an Honorary Secretary of the
© 1985 Brian Jones British Astronomical Association and a
Picture credits © 1985 as acknowledged
member of the American Association of
on page 224
Variable Star Observers. He is a writer on
This book is set in Century Schoolbook
astronomy and meteorology and has also
Corgi Books are published by
Transworld Publishers Ltd, recently completed a major translation
Century House, 61-63 Uxbridge Road, from the German, Variable Stars, to be
Ealing, London W5 5SA published in spring 1985. His other
Reproduced by Chelmer Litho Productions, interests are planetary geology and
Maldon, UK meteorological photography.
Typeset by MS Filmsetting Ltd, Frome, UK
Printed and bound in Belgium by Usines
Brepols SA Brian Jones is an amateur astronomer
with 25 years’ experience. As secretary
Conditions of sale and founder member of the Bradford
This book shall not, by way of trade or otherwise, be lent, resold, Astronomical Society, he is involved in
hired out or otherwise circulated without the publisher’s prior
consent in any form of binding or cover other than that in which it radio and television broadcasting. He has
is published and without a similar condition including this edited a variety of astronomical journals,
condition being imposed on the subsequent purchaser. This book is
published at a net price and is supplied subject to the Publishers including the Handbook for Astronomical
Association Standard Conditions of Sale registered under the Societies for the Federation of
Restrictive Trade Practices Act, 1956.
Astronomical Societies, and contributes
articles on astronomy to popular-interest
The three sections of the book were
magazines. His recent work is aimed at
contributed -
fostering an interest in astronomy among
The Daylight Sky by Storm Dunlop a younger audience.
The Night Sky by Colin A. Ronan
Observing and Recording the Sky by
Brian Jones
Editor: Jonathan Hilton
Managing Editor: Ruth Binney
Assistant Editors: Louise Tucker
Gwen Rigby
A,rt Director: Paul Wilkinson
Picture Editor: Zilda Tandy
Production: Barry Baker, Janice Storr
C O N T E N T
Introduction 6 The Moon 114
The stars 120
Part I THE DAYLIGHT SKY The Galaxy 124
The sky above 10 The constellations 132
The sky’s colours 14 Star magnitudes 138
Optical phenomena 20 Star watching 142
Wind movements 30 Guidance for observers 158
Water in the atmosphere 40 Nebulae and clusters 160
Cloud watching 44 Double and variable stars 166
Cloud varieties 46 Shooting stars and comets 170
Nature’s fireworks 60 Artificial satellites 176
The Sun 70
Mirages 78 Part III OBSERVING &
Nacreous and noctilucent RECORDING THE SKY
clouds 80 The naked eye 182
Aurorae 82 Photographing the
The sky from above 84 daylight sky 184
Weather lore 90 Photographing the
Building a weather station 92 night sky 188
Binoculars 192
Part II THE NIGHT SKY Telescopes 196
Approaching the sky 100 Telescope mounts
The Solar System 102 and drives 198
Mercury and Venus 104 The home observatory 200
Mars 106 Keeping records 202
Jupiter 108 Appendices 204
Saturn 110 Glossary 216
Uranus, Neptune Index 220
and Pluto 112 Acknowledgements 224
N T R O D U C T O
The sky remains the most reliable The two great sciences arising from
source of the best things in life that the study of the skies are meteorology
are free. The Moon does, indeed, be­ and astronomy. The original word for
long to everyone. So do rainbows, meteorology was coined by Aristotle
shooting stars, eerie eclipses and to describe atmospheric conditions,
breathtaking sunsets. Although the and now relates particularly to wea­
sky’s most dramatic phenomena do ther forecasting. Astronomy derives
not occur every day, it is still true from another ancient Greek word
that, wherever you are, what takes meaning star-arranging. It is gener­
place in any 24-hour period in the sky ally associated with the sky at night -
will provide substantial interest to when heavenly bodies are most easily
the skywatcher who has learned to observed. Both studies can, of course,
interpret it. be a life’s work; but equally, both can
Observation of the sky was vital to make rewarding leisure pursuits, open
ancient people - not only the learned, to all. A healthy curiosity and a little
but shepherds, farmers, fishermen and patience are enough to qualify you for
sailors, who relied on the information skywatching.
it gave them day and night. Even Just as the Earth has its seasonal
today, these same groups of people rhythms, so the sky has its own dis­
have a vested interest in skywatching, tinct pattern, with characteristics
and are enviable for the knowledge unique to dawn, full daylight, evening
that seems just to come naturally. But and dark. The first two sections of this
we can all share in it if we want to. handbook are devoted to exploring the
The sky is a recreational resource far day and night skies. The Daylight Sky
too many people miss out on. Anyone will give you the basics of meteorology
who finds himself remarking on the so that'you can make sense of weather
weather (and that means everyone) is maps, identify the form and movement
a potential skywatcher. of the clouds and the direction of the
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wind, and attempt some predictions of make your observations permanent;
your own. Here you will find every­ they could be of real scientific value
thing from building your own weather (comets West, Bennett and Alcock are
station to the significance of a full among those bearing the names of
solar eclipse. their amateur discoverers). Here we
In The Night Sky, even the city describe the best ways to photograph
dweller, plagued by artificial lighting, the day and night sky, as well as how
will find help in picking out the more to build and equip your own home
spectacular astronomical sights, from observatory.
the readily perceived phases of the The more you skywatch, the more
Moon to the changing pageant of the useful you will find the Appendices,
constellations. Familiarity with the which are full of key dates for celestial
planets is enormously satisfying; Mer­ events, essential statistics and even
cury and, especially, Venus (the Morn­ details of societies of amateur meteor­
ing and Evening Stars) can be magni­ ologists and astronomers you would
ficent in twilight and early evening. be welcome to join. Their enthusiasm
Jupiter, too, is a wonderful sight in and assistance can enrich your sky­
the night sky, considerably enhanced watching considerably. The sky is, in
by viewing it through binoculars. every sense, an immense subject, but
Meteors - the shooting stars of earlier it is also a generous and constantly
times - comets, galaxies and the multi­ accessible one. It is hoped that with
tude of stars that can be seen with a the help of this book you can meet it
telescope or the naked eye are all dealt half-way
with in The Night Sky.
The third section of this handbook
concerns itself with Observing and
Recording the Sky. Your sky watching
takes on greater meaning when you Colin A. Ronan, MSc FRAS
7

THE DAYLIGHT SKY
The sky above/1
Km
It is hard to believe, when looking up
into the sky, just how thin is the layer
of atmosphere surrounding the Earth.
The 'top’ is usually described as being
about 60 to 80 km (38 to 50 mis) above
the surface, only about one-hundredth
of the Earth’s radius at the Equator -
6,378 km (3,963 mis).
There is, in fact, no true upper
boundary to the atmosphere, but there
is a transitional region where it
merges into interplanetary space.
This region is greatly affected by
changes that occur during the solar
cycle (see pp 70-7).
Atmospheric pressure is an import­
ant factor in governing the behaviour
of the weather and also in its predict­
ion (see pp 90-1). This pressure is the
weight of the column of air above any
particular point and is measured by
one of the various types of barometer.
Pressure was originally described in
terms of the height of the column of
mercury it would support, but it is now
defined in scientific units as the force
exerted on a given area. Atmospheric
pressure is normally measured in mil­
libars (mb), or thousandths of a bar.
One bar is equivalent to the pressure
exerted by 750.06 mm (29.53 in) of mer­
cury at 0°C (32°F). Although pressure
is by no means constant throughout
the atmosphere, the average at sea
level is about 1013 mb.
In the atmosphere as a whole, pres­
sure declines upward, at first rapidly
and later much more gradually. When
you fly in an aircraft at a height of
about 9 km (approximately 30,000 ft),
the outside pressure is around 350 mb.
This is a measure of the amount of air
above you - roughly 65 per cent of the 8 _
atmosphere lies below. Troposf
6 “
Temperature also varies through­
4 -
out the atmosphere and the way in
which it changes with height is used to 2 -
0 -
define the various layers. The lowest
layer, the troposphere, contains most
of the mass of the atmosphere and
here, too, the changes that form the
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