Practical Astronomy. A User-Friendly Handbook for Skywatchers

234 Pages·1994·33.132 MB·English

by  H.R. Mills (Auth.)

Dedicated to Ida my wife for her devoted help and
forbearance throughout.
PRACTICAL ASTRONOMY:
A User-friendly Handbook
for Skywatchers
H. ROBERT MILLS, OBE, MSc, MIEE, CEng, DipEd, FRAS
Formerly Director of Science and Engineering, The British Council, London
Albion Publishing
Chichester
First published in 1994 by
ALBION PUBLISHING LIMITED
International Publishers, Coll House, Westergate Street, Aldingbourne, Chichester,
West Sussex, England
USA: PAUL & COMPANY PUBLISHERS' CONSORTIUM INC., P.O. Box 442,
Concord, MA 01742
Reprinted 1995, 1997, 1998 (twice), 2000
COPYRIGHT NOTICE
All Rights Reserved. No part of this publication may be reproduced, stored in a retrieval
system, or transmitted, in any form or by any means, electronic, mechanical,
photocopying, recording, or otherwise, without the permission of Albion Publishing,
International Publishers, Coll House, Westergate Street, Aldingbourne, Chichester, West
Sussex, England.
© 1994 H. Robert Mills/Albion Publishing
British Library Cataloguing in Publication Data
Mills, H. Robert
Practical Astronomy: User-friendly
Handbook for Sky watchers
I. Title
522
ISBN 1-898563-02-0 (Albion Publishing) Library Edition
ISBN 1-898563-00-4 (Albion Publishing) Paperback Edition
Typeset by Warren White Typesetting, Chichester
Printed and bound in Great Britain by MPG Books Ltd, Bodmin, Cornwall
Foreword
by Dr Heather Couper, Professor of Astronomy, Gresham College, London
I don't think I've ever seen Robert Mills without a device. Let me explain: at
astronomical gatherings, Robert is there in a comer (surrounded by people, of
course), busily demonstrating some (apparently) fiendish complex — er, device.
It could be a planisphere, a flat representation of the sky; it might be a
navigational instrument like a sextant; a pendulum; even a modem version of
the old Arab star-finder, the astrolabe. One day he turned up with a can of lager
— only to turn it into a very ingenious sundial!
Robert Mills thinks astronomy is fun. And as a highly experienced educator,
he also knows that it is arguably the most important of all the sciences. Most
people, including the young, have an instinctive fascination for astronomy. Many
can recite the order of the planets in the Solar System long before they're seven
or eight. It's well-known that astronomy is a sugar-coated pill that lures young-
sters into studying less immediately attractive sciences like physics and chem-
istry. And I needn't labour the point about how much we need young scientists
in the future.
Astronomy now forms part of the Curriculum in most English and Welsh
schools. All very well, if it helps produce our next generation of scientists, but
how do you go about teaching it? If you're a teacher, you need all the help you
can get — and this book will certainly give you some ideas. The great thing
about this Handbook is that it's all hands-on. Some of the gadgets may look
complicated, but persevere—because you'll find they're a marvellous way of
making astronomy applicable and down-to-earth. But, I hear you say, "astrono-
mers do it at night" —while schools "do if'during the day. However, dozens
of Robert Mills' projects are exclusively designed for daytime work, and there-
fore ideal for the classroom.
For those already bitten by the astronomy bug, read on—there's plenty in
here for you too. Quite apart from some very practical advice on telescopes,
6 Foreword
making measurements, using starcharts and understanding lenses, there's enough
to keep you busy for a whole string of cloudy nights.
And that brings me back to a point I remember Robert making. "What would
life be like," he asked, "if the sky were perpetually clouded, so that we saw
no Sun, no Moon and no stars — in other words, no astronomy?" And he went
on to answer the question: "We would then have no means of telling the time,
no clocks, no calendars, no compass directions, no exploration, no navigation,
no communal life".
And who said that astronomy wasn't a practical subject?
Heather Couper
July 1993
Preface
' Ί listen and forget, I see and I learn, I do and I understand. ' '
(Chinese proverb)
The object of this book is to help people o fall ages and their teachers, to engage
in skywatching as an enjoyable and worthwhile pursuit that can enliven and
enrich programmes of other sciences including mathematics! Modern astronomy
is involved to some degree in practically all branches of science and these can
be listed under the three headings shown in the Table on page 3. This list is
not complete and there are other systems of classification, but it supports the
view that astronomy has a rightful and valuable educational role to play in
modern curriculum development.
So, astronomy draws richly on the sciences in promoting our understanding
of the Universe. Inevitably it reciprocates and feeds back valuable and stimu-
lating contributions to the advancement of science, particularly in Physics,
Chemistry, Mathematics, Geology and Meteorology. Our nearest star, the Sun,
and stars in their various stages of evolution have provided us with exciting
evidence for modern theories of atomic structure. The sun is a large nuclear
pressure cooker that produces vast amounts of radiant energy and streams of
atomic and subatomic particles. We learn through curiosity and interest by asking
questions, seeking answers and, above all, by doing. Rudyard Kipling comes to
mind here:
/ keep six honest serving men
(They taught me all I knew);
Their names are what and why and when
and how and where and who.
Whilst reading and using this book we should not lose sight of the awe and
wonder and mystery of our Universe. Astronomy is a subject fraught with many
facts and theories that, to the human mind, are quite beyond our understanding
8 Preface
or belief. The Big Bang theory, derived apparently from a mysterious extrapo-
lation of specially devised Mathematical Physics, expects us to believe at the
present time that all the matter in the Universe at some primaeval instant about
eighteen thousand million years ago was concentrated at infinite density in a
space of zero volume. This object, or singularity, of mass 1050 tonnes exploded
and may reach the boundaries of space, as we are led to believe, some
5 x 1012 years later at speeds approaching that of light. Eddington, the great
Astronomer, was once asked after a lecture on the vastness of our Universe,
"Sir, is it not a fact that astronomically speaking man is but an insignificant
speck in the universe?'' To which Eddington replied, "Astronomically speaking
man is the Astronomer"
Brother Lawrence, a Franciscan monk, described a religious person as one
who
"Practices the presence of God".
A dedicated astronomer is correspondingly one who
"Practices the presence of the Universe"
So let us not be discouraged or over-awed but stimulated and heartened when
we contemplate things that are at present beyond our understanding. When we
attempt to do things as sky watchers we are participating in the oldest of the
sciences.
A study of the history of mankind reveals how astronomy has profoundly
influenced the course of civilisation from Neolithic times (about 100,000 years
ago) when man began to use the stars to fix the times for people to sow and
plant crops and for hunters and animals to migrate. For a moment, reflect what
life would be like now if our sky had been permanently overcast by clouds
obscuring completely the sun, moon and stars; we should have had no means
of making calendars, fixing dates, holding festivals or telling the time. There
would have been no widespread sense of direction, no exploration or navigation.
One of the most exciting sea stories from the 1st century AD is that told by St
Paul, about his voyage in a grain ship from Sidon to Rome, a voyage which
nearly ended in complete disaster, because the navigators could not use the sun
or the stars to get their bearings, as verse 20 of the 27th Chapter of Acts of the
Apostles relates:-
' '. and when neither sun nor stars shone upon us for many days, all hope that
we should be saved was taken away. ' '
They could not use the sun or stars for navigating their ship. They were lost in
the Mediterranean.
Preface 9
THE MAIN BRANCHES OF ASTRONOMY
Descriptive Gravitational Physical
History Dynamics Composition of stars
The Ancient world Kepler's Laws Abundance of elements
Megalithic sites Newton's Laws Origin of stars and planets
Calendars Organic chemical molecules in space
Astrolabes Orbits under central forces The origin of life
Star catalogues Prediction of positions Evolution
Positions of all celestial Distances Earth science
bodies
Momenta Geology
Instruments Masses of celestial bodies Age and stellar evolution
Telescopes:- optical, radio Sizes White Dwarfs, Red Giants
Cameras and photography Densities Heat and energy production
Sundials Cosmology Temperature of stars
Clocks-sidereal time Relativity Radioactivity
Navigation by stars Gravitational forces in Interstellar space
stars' interiors
Astrolabes Tides Plasma-physics
Scientific electronic Nuclear chemistry
calculation
Computers Fundamental particles
Stellar magnitudes Spectroscopy The radiation
Colour spectrum from g-rays to radio
waves
Star clusters Quasars
Galaxies Pulsars - red shift
Earth science Black holes
Geography Time measurement
Plaets Propagation of light
Astronomical objects in Doppler effect
works of art
The impact of astronomy Relativity
on religious thought and Aberration
philosophy
The Big Bang or the Creator. Magnetic and electric fields in
space
The solar wind
These three branches are closely linked so that each one depends for its advance on research and
discoveries in the other two.
In latitudes about 53° N (North) during midsummer, we have only about four
hours of real darkness around midnight, and in mid-winter, although we have
eighteen hours of dark sky watching, many opportunities for good ob-
serving are ruined by adverse climatic conditions or bright city lights. ' 'Practical
Astronomy" attempts to provide a variety of things to make and study in those
intervals when the sky is impenetrable or fingers frozen, so as to be ready for
10 Preface
a full and rewarding outdoor practical programme with telescopes, binoculars,
theodolites and star charts, as soon as conditions are favourable.
However astronomy can also be studied in a practical way during the daylight
hours, the sun, our nearest star, can give us many things to do i ndaylight both
in the classroom and at home that are instructive and easy to carry out, and
provide a valuable insight into our place on earth — as a space ship concerning
our place in the solar system, and the nature and positions of other stars in our
Galaxy. Most young skywatchers look with envy on astronauts who are privi-
leged to take trips in a space ship; but think for a moment. We are now on a
spaceship! The Earth on which we are fortunate to be is a marvellous spaceship,
in orbit round the Sun, with all 'mod cons' laid on for our comfort; oxygen,
comfortable temperature and air pressure and gravity that suits life perfectly!
We can often gaze with wonder and enjoyment all round at the stars, galaxies,
sun, moon and planets. Enjoy the privilege of being on a spaceship.The activities
described in this book, will include:
• Using the sun to mark our base line, the N-S meridian;
• The construction of sundials of various kinds;
• The times and positions of the Sun at it rsising and setting;
• The tilt of the earth's axis;
• The Sun's irregularities in keeping good time;
• Sunspots, flares and the sun's spectrum;
• Finding and identifying stars.
Although skywatchers are often called 'star-gazers', and the sun is a star, it is
for us a very special star — at the centre of our solarsystem (2.2) it is so near
that we must never gaze directly at it for to do so would permanently
damage our eyes. The human eye contains a powerful and beautiful little lens
that focuses the sun's light and heat on the retina. The heat unrestrained is
sufficient to burn the delicate network of sensitive nerves. Try this powerful
heating effect by using a magnifying glass to focus an image of the sun on a
piece of paper: the paper will soon smoulder and burn. The sun's rays are so
strong that if they were to fall on a lens-like piece o fglass in a dry region, they
could start a fire as has often happened.
No mathematics teacher need be short of examples or projects in astronomy
for exercises with a calculator. Astronomy can, and should, be used as a basis
for an integrated science programme in view of the present absorbing interest
in space probes, moon landings, lasers, black holes, radio and television pro-
grammes on astronomy.
Astronomy, however, can be successfully introduced into a science programme
only if presented and received with understanding and enjoyment. Beware of
Preface 11
the disaster that follows bad teaching and learning without understanding as
exemplified by the boy who in answer to the question:
' What causes the tides? ' '
wrote, without proper understanding:
' The tides are caused by the rays of the moon striking the surface of the sea
at an angle of 23.5° Fahrenheit"!
Many of the "Things to do" in this section have explanatory notes that may
appear to stray into subject areas that are only marginally the province of
astronomy. This is in keeping with the expressed object of the book, and in the
hope that teachers of other disciplines, listed under the heading "Descriptive
Astronomy" in the Table on page 9, will draw extensively on astronomy for
examples and projects which can be a source of interest and excitement to young
people in this space age.
ACKNOWLEDGEMENTS
I would like to express my thanks to many members of the British Astronomical
Association, and the Association for Astronomy Education who have given the
encouragement and helpful advice on my assembly o ftopics for this Handbook,
many of which have been demonstrated at meetings o fthese Associations. I am
particularly indebted to Commander Henry Hatfield, past President of the B.A.A.
and to Eric Zucker, Editor of the A.A.E. Journal and Newsletter. I am greatful
to Eddy Butt for his help with photographs, to Myra Newton for her skillful
typing, and to John Carden for his initial typesetting work.
I wish to thank Ellis Horwood of Albion Books for this friendly help and
cooperation in getting this book published. This is the outcome of over sixty
years of friendship from our early days in India (Madras) when we collaborated
in producing several books on Science for schools in India: he with Macmillan's
Madras House, India, and I with the University of Madras. After the War, he
inspired and helped me to produce my book on Teaching and Training. Through-
out the years we and our families have remained close friends.