Astronomy with a Home Computer

207 Pages·2005·5.986 MB·English

by  Neale Monks (auth.)

Patrick Moore’s Practical Astronomy Series
Other titles in this series
Telescopes and Techniques (2nd Edn.) Solar Observing Techniques
Chris Kitchin Chris Kitchin
The Art and Science of CCD Astronomy Observing the Planets
David Ratledge (Ed.) Peter T. Wlasuk
The Observer’s Year Light Pollution
Patrick Moore Bob Mizon
Seeing Stars Using the Meade ETX
Chris Kitchin and Robert W. Forrest Mike Weasner
Photo-guide to the Constellations Practical Amateur Spectroscopy
Chris Kitchin Stephen F. Tonkin (Ed.)
The Sun in Eclipse More Small Astronomical Observatories
Michael Maunder and Patrick Moore Patrick Moore (Ed.)
Software and Data for Practical Astronomers Observer’s Guide to Stellar Evolution
David Ratledge Mike Inglis
Amateur Telescope Making How to Observe the Sun Safely
Stephen F. Tonkin (Ed.) Lee Macdonald
Observing Meteors, Comets, Supernovae and Astronomer’s Eyepiece Companion
other Transient Phenomena Jess K. Gilmour
Neil Bone Observing Comets
Astronomical Equipment for Amateurs Nick James and Gerald North
Martin Mobberley Observing Variable Stars
Transit: When Planets Cross the Sun Gerry A. Good
Michael Maunder and Patrick Moore Visual Astronomy in the Suburbs
Practical Astrophotography Antony Cooke
Jeffrey R. Charles Astronomy of the Milky Way: The Observer’s
Observing the Moon Guide to the Northern and Southern Milky Way
Peter T. Wlasuk (2 volumes)
Deep-Sky Observing Mike Inglis
Steven R. Coe The NexStar User Guide
AstroFAQs Michael W. Swanson
Stephen F. Tonkin Observing Binary and Double Stars
The Deep-Sky Observer’s Year Bob Argyle (Ed.)
Grant Privett and Paul Parsons Navigating the Night Sky
Field Guide to the Deep Sky Objects Guilherme de Almeida
Mike Inglis The New Amateur Astronomer
Choosing and Using a Schmidt-Cassegrain Martin Mobberley
Telescope Care of Astronomical Telescopes and
Rod Mollise Accessories
Astronomy with Small Telescopes M. Barlow Pepin
Stephen F. Tonkin (Ed.)
Astronomy
with a Home
Computer
Neale Monks
With 87 Figures
Cover illustration: Front cover computer image courtesy of Apple Computer. Unauthorized use not
permitted.
British Library Cataloguing in Publication Data
Monks, Neale
Astronomy with a home computer.–(Patrick Moore’s
practical astronomy series)
1. Astronomy–Data processing–Popular works 2. Astronomy–
Computer programs–Popular works 3. Imaging systems in
astronomy–Popular works
I. Title
522.8′4
ISBN 1852338059
Library of Congress Cataloging-in-Publication Data
Monks, Neale.
Astronomy with a home computer / Neale Monks.
p. cm. – (Patrick Moore’s practical astronomy series,
ISSN 1617-7185)
Includes bibliographical references and index.
ISBN 1-85233-805-9 (alk. paper)
1. Astronomy–Data processing. I. Title. II. Series.
QB51.3.E43M64 2004
522′85–dc22 2004050425
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sent to the publishers.
Patrick Moore’s Practical Astronomy Series ISSN 1617-7185
ISBN 1-85233-805-9
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Preface
Amateur astronomy can be a surprisingly aggressive field. Newcomers to the
hobby will often find their computerized telescopes derided as little more than
children’s toys, equipped with digital crutches for people too lazy to learn the sky
the traditionalway. Apparently, looking at the Moon from your front porch isn’t
seriousastronomy, and what you should be doing is driving three hundred miles
out into the countryside and working your way through a catalog of magnitude-
fifteen galaxies. Otherwise reasonable people will insist that if you look at the
faint fuzzy ball properly, you can’t help but see the chains of stars running
through that globular cluster breathtakingly like a squadron of herring gulls
following a fishing trawler. Maybe, maybe not, but with all the hoopla over
apochromatic refractors and wide-angle eyepieces, the star charts down to
thirtieth magnitude and CCD cameras that cost more than small motor cars,
some people have forgotten that amateur astronomers look at the night sky not to
do science but simply for the fun of it. Moreover, one of the best tools for enhanc-
ing that fun is probably sitting somewhere in your house right now: the home
computer.
However, beyond CCD astrophotography, astronomy books and magazines
tend to ignore this particular adjunct to the hobby. This book is my attempt to
rectify this, to put as many ideas and tips into one volume as possible, from
webcam astrophotography to writing equipment reviews for astronomy web sites.
One of my main aims throughout this book has been to keep everything as acces-
sible as possible, the only common denominator being a telescope and a home
computer. Even a go-to telescope, while useful, isn’t a prerequisite. This isn’t a
computer manual either, and while there are tips on using computers more
efficiently where it relates to amateur astronomy, there isn’t anything on how to
install programs or write HTML code. Finally, this isn’t a book just for users of
any one particular kind of computer; in virtually all cases the projects described
in this book can be accomplished equally well with Windows, Macintosh and
Linux. There’s no one best operating system any more than there is a perfect
telescope design.
Many people have contributed freely of their time and experience and, without
them, writing this book would have been impossible. Particular thanks goes to
the software developers who have shared their programs with me and explained
something of the philosophy behind their projects. Chief among these are Milton
Aupperle (Outcast Software), Elwood Downey (Clear Sky Institute), Jason Harris
(KStars), Stephen Hutson (American Dream Partnership), Steve McDonald
(Silicon Spaceships), Paul Rodman (Ilanga Software) and Darryl Robertson
(Microprojects). Celestron, IBM, Logitech, Meade, Tele Vue and Vixen have been
generous with their time and resources, and their help in supplying images in
v
vi Preface
particular is appreciated. Artist and web designer Michele Kraft shared her expe-
rience and advice with me while compiling the sections on web publishing and
graphic design. My personal thanks must go to David Schultz, editor of the
AppleLust web site, who facilitated many of the opportunities I had to review
astronomical software and accessories over the years. Thanks also to my friend
and colleague at the Natural History Museum in London, Phil Palmer, who
helped with the section on photography, and to John Watson at Springer-Verlag
for helping shepherd this project through to completion.
Neale Monks
Lincoln, Nebraska
USA
Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
2 Modern Amateur Astronomy and the Internet . . . . . . . . . . . . . . . . . . . . . . . . . 21
3 Planetarium Programs and Other Astronomical Software . . . . . . . . . . . . . . . 35
4 Buying a Go-To Telescope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
5 Using and Enjoying Your Telescope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111
6 Webcam and Digital Camera Astrophotography . . . . . . . . . . . . . . . . . . . . . . 137
Appendix 1: Reading and Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185
Appendix 2: Seeing, Transparency and Darkness . . . . . . . . . . . . . . . . . . . . . . . . 197
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201
vii
CHAPTER ONE
Introduction
There can be little doubt that computers revolutionized amateur astronomy
through the 1990s in the same way as mass-produced Schmidt–Cassegrain (or
SCT) telescopes did in the 1970s and high-quality wide-angle eyepieces did in the
1980s. At the time the first reasonably priced SCTs went on sale in the early 1970s,
the dominant hobbyist telescope was the equatorially mounted Newtonian
reflector. While a fine instrument optically, this design tends to be large, unwieldy
and fiddly to maintain. Advocates of the SCT pointed out the much more
compact shape of that design coupled with the fork mounting made it a much
easier telescope to use, transport and store, and one that required far less mainte-
nance to work well. Critics pointed out that the average commercially produced
SCT was more than twice as expensive as a comparably sized Newtonian, and in
the opinions of many delivered poorer images. Nonetheless, many hobbyists
placed convenience and ease of use over both cost and sheer optical performance,
and the 200-mm (8-inch) Schmidt–Cassegrain remains one of the most popular
telescopes for intermediate and advanced amateur astronomers the world over.
They may not be the best telescopes in terms of sheer optical prowess, but for
many hobbyists they occupy a sweet spot as far as balancing cost, convenience
and ease of use are concerned.
If the SCT was the big thing in the 1970s, then wide-angle eyepieces such as
those produced by Al Nagler’s fledgling optics company Tele Vue caught the con-
spicuous consumption mentality of the 1980s. They were then, and remain now,
expensive pieces of kit aimed primarily at advanced hobbyists; for example, the
top of the line 31-mm Nagler wide-angle eyepiece costs more than the Meade
ETX 90 go-to telescope. However, what these wide-angle eyepieces offered was a
new way of looking at the sky. With traditional eyepieces like Plössls, the field
of view is narrow, that is, around the 50˚ mark or less, and so relatively low
1
2 Astronomy with a Home Computer
Figure 1.1.No other
telescope design
combines performance,
price and compactness
as well as the
Schmidt–Cassegrain
telescope(photo courtesy
of Celestron).
magnifications are needed if large objects such as open star clusters are to be seen
in their entirety. Wide-angle eyepieces have fields of view from 60˚ to 84˚, and so
at any given focal length reveal a much larger area of sky than a traditional eye-
piece. The result was that it was now possible to view big objects at high
magnifications, and so discern subtle details while retaining the visual impres-
siveness of seeing the entire object at once. Almost without exception, these wide-
angle eyepieces worked wonderfully well with the short focal length Newtonians
and refractors that became popular at the same time, unlike the more traditional
eyepiece designs. Stars were sharp to the edge of the field, and when used on the
planets, colors and contrasts were just as striking. In a virtuous circle of supply
and demand, many different manufacturers competed to produce ever better eye-
pieces and telescopes for the increasing numbers of amateur astronomers who
were prepared to spend substantial amounts of money to get the best possible
views of the night sky.
The SCT had given the hobby a reasonably priced but compact instrument
ideal for backyard astronomers, and the burgeoning range of top-notch eyepieces
meant that users could get great views of solar system and deep sky objects, but
there still remained the problem of finding things to look at. The Moon is an
obvious enough target, and so are, generally speaking, the planets, the more
interesting of which are usually brighter than any star; but most double stars and
deep sky objects are too faint or inconspicuous to be seen with the naked eye, and
for beginners, finding these hidden treasures can be difficult. The received
wisdom was that the best thing for newcomers to the hobby to do was to learn the
sky the old-fashioned way. Essentially this came down to learning the sky as if it
were a map. At first, you would begin to learn the names of the brightest stars,
and from those you could make out the constellations. Using these patterns to
aim your telescope in the right general direction, you would then consult a star
chart or atlas to help identify fainter stars to act as landmarks showing the way to
the desired deep sky object. This technique, star hopping, works well after some
practice and a number of books are available to introduce the technique to those
new to it; some favorites of mine are listed in Appendix 1. An alternative method
relies on mechanical aids called setting circles. Most commonly, these are discs
Introduction 3
Figure 1.2.Although wide-angle eyepieces of various types had been around for years, it
wasn’t until the 1980s that companies like Tele Vue began to market highly corrected ones
providing the flat, sharp field ideally suited to observing star clusters and lunar landscapes
(photo courtesy of Tele Vue Optics, Suffern, NJ).
placed around the two axes of an equatorial telescope mount, one marked off in
units of declination and the other in right ascension, and so matching the coordi-
nate system used to describe points in the sky. Provided that the telescope is
properly aligned to begin with, meaning that the right ascension axis is pointing
along the Earth’s north–south axis of rotation (i.e., towards Polaris or Sigma
Octanis depending on your hemisphere), then the setting circles can be used to
“dial up” faint objects without any need to know the sky. In practice though,
beginners are apt to find setting circles more trouble than they are worth: on the
lower-cost telescopes they tend to be rather crude to begin with, and if the tele-
scope isn’t completely stable then the movements in declination and right ascen-
sion become too inaccurate to be useful. The more expensive heavy-duty mounts
(such as those from Vixen and Losmandy) are much more stable and the setting
circles more accurately made and easier to use – but these mounts cost more than
the average beginner is likely to spend on a complete telescope set-up, including
tripod, mount and eyepieces. Even with the deluxe tripods, between the need for
spot-on polar alignment at the start of an observing session and then having to
read the small numbers on the setting circles in the dark when moving between
targets, many skilled amateurs find setting circles a bit heavy going at times.