Astrophotography

241 Pages·2014·26.482 MB·English

by  Thierry Legault

Astrophotography
Thierry Legault is a world-renowned astrophotographer. In 1999, Legault received the
prestigious Marius Jacquemetton prize from the Societe Astronomique de France for his
astronomical photographs. He is so highly regarded in this industry that the International
Astronomical Union officially bestowed the name Legault on asteroid #19458.
Legault co-authored the book New Atlas of the Moon (Firefly, 2006) and has written
numerous articles about astrophotography for French and American magazines. He regu-
larly presents courses and gives astrophotography lectures in Europe, America, and Asia.
Legault’s images, most notably those of the International Space Station, have been
published and broadcast worldwide, including in NASA publications, Nature, Scientific
American, The Times, The Wall Street Journal, Popular Science, Aviation Week, as well as on
numerous television stations including The Discovery Channel, BBC, CNN, ABC, CBS, Fox,
CBC, and MSNBC.
Thierry earns his living as an engineer and is currently living in the suburbs of Paris,
France.
For more information visit www.astrophoto.fr
Thierry Legault
Astrophotography
Editor: Joan Dixon
Translation: Alan Holmes and Thierry Legault
Copy editor: Judy Flynn
Layout: Petra Strauch
Cover Design: Helmut Kraus, www.exclam.de
Printer: Friesens Corporation
Printed in Canada
ISBN: 978-1-937538-43-9
1st Edition 2014
© 2014 Thierry Legault
Rocky Nook, Inc.
802 E. Cota Street, 3rd Floor
Santa Barbara, CA 93103
www.rockynook.com
Original French title: Astrophotographie, 2nd Edition
© 2013 Groupe Eyrolles, Paris, France
Library of Congress Cataloging-in-Publication Data
Legault, Thierry, author.
Astrophotography / by Thierry Legault. -- 1st ed.
pages cm
ISBN 978-1-937538-43-9 (softcover : alk. paper)
1. Astronomical photography. 2. Photography--Digital techniques. I. Title.
QB121.L44 2014
522'.63--dc23
2013040681
Distributed by O‘Reilly Media
1005 Gravenstein Highway North
Sebastopol, CA 95472
All rights reserved. No part of the material protected by this copyright notice may be reproduced or utilized
in any form, electronic or mechanical, including photocopying, recording, or by any information storage and
retrieval system, without written permission of the publisher.
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are claimed as trademarks of their respective companies. Where those designations appear in this book,
and Rocky Nook was aware of a trademark claim, the designations have been printed in caps or initial caps.
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While reasonable care has been exercised in the preparation of this book, the publisher and author
assume no responsibility for errors or omissions, or for damages resulting from the use of the information
contained herein or from the use of the discs or programs that may accompany it.
This book is printed on acid-free paper.
All astronomical images in the book are by Thierry Legault and may not be reproduced without the author's
express written premission.
ACKNOWLEDGEMENTS
Acknowledgements
I wish to thank Alan Holmes at Santa Barbara Instrument particular Arnold Barmettler (CalSky), Chris Peat (Heavens-
Group (SBIG) for his generous and essential help with Above), Tony Philips (spaceweather.com), Christian Buil
translating this manuscript from French to English. Thanks (IRIS), Cyril Cavadore (PRISM), and Jean-Philippe Cazard
also to Michael Barber and Alan at SBIG for their pivotal (Astrosurf). I owe special thanks to Christian Buil, who
contribution in initiating my contact with Rocky Nook pub- gave me the desire to get into digital photography and
lishing and facilitating further discussions. helped me succeed through his CCD cameras, software,
I would like to thank Rocky Nook Publishing, and es- and writings that have taught me so much.
pecially Joan Dixon, for their confidence in this book and I also thank the many distributors who have put their
their commitment to seeing it through to publication. I equipment at my disposal for the photographs in this book:
appreciate the excellent job they have done with the new Médas Instruments (Vichy, France), Optique Unterlinden
layout and preparation of the manuscript. (Colmar, France), and La Maison de l’Astronomie (Paris,
I also would like to thank Arnaud Frich for proposing the France). I thank Rémi Petitdemange and Richard Galli
idea of t his book to me and to Eyrolles [the publisher of (Optique Unterlinden), Thomas Maquaire (Nikon France),
the original French edition], and for his valuable assistance Vincent Hamel (Meade France), Scott Roberts (Explore
in acquiring the photographs of astronomical equipment Scientific), Corey Lee and Bryan Cogdell (Celestron), and
presented here. I further thank Eyrolles for offering me the Nick Hudson (True Technology Ltd).
opportunity to achieve this idea with total freedom in my I must acknowledge the contribution of my course
choice of design and content. I especially thank my editor, trainees and all amateurs who, with their relevant ques-
Stéphanie Poisson, for her patience, kindness, guidance, tions over the years, helped me to compose this book so
and careful proofreading. that the answers flow as clearly as possible. I also thank all
I must mention the pioneers of film and digital astro- the amateurs who have given me words of encouragement
photography, those for whom boundaries were made to online and during conferences, meetings, and workshops.
be overcome, particularly Jean Dragesco, Christian Arsidi, Many people from all around the world have helped me
Gérard Thérin, Christian Viladrich, Donald Parker, Robert photograph celestial wonders, especially François Colas,
Gendler, and Damian Peach. The authors who passed on Jean-Luc Dauvergne, and the staff of the Kennedy Space
to me the desire to observe and photograph the sky, in- Center. I have been helped by many people and organiza-
cluding Pierre Bourge, Jean Dragesco, Serge Brunier, Patrick tions who aided my quest to photograph the southern
Martinez, and Guillaume Cannat, also were essential to sky and several total eclipses under the best conditions,
my success in astrophotography. particularly Serge Koutchmy, Jaime Vilinga, the Ministry
I owe a debt of gratitude to all the software developers of Research and Technology of Angola, and the University
and webmasters who have given us the means to plan our of Luanda, as well as all those who warmly welcomed us
imaging sessions and to make the most of our images, in in Tchivinguiro, Angola.
v
Table of Contents
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v Chapter 3
Foreword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ix Image Calibration and Compositing . . . . . . . . . . . . . . 41
How to Read This Book . . . . . . . . . . . . . . . . . . . . . . . . . . . . xi The Components of an Image . . . . . . . . . . . . . . . . . . . . . . 43
The Thermal Signal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
Chapter 1 The Bias Signal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
Astrophotography without a Telescope . . . . . . . . . . . 1 Uniformity Defects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
Cameras and Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 The Causes and Properties of Uniformity
Camera Mounts and Settings . . . . . . . . . . . . . . . . . . . . . . 4 Defects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
Astronomical Subjects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Calibration of an Image . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
Planetary Conjunctions . . . . . . . . . . . . . . . . . . . . . . . . . 5 Correction of the Thermal Signal . . . . . . . . . . . . . . . 46
Constellations and the Milky Way . . . . . . . . . . . . . . 6 Correction of the Uniformity Defects . . . . . . . . . . . 47
Comets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Image Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
Star Trails . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Noise and Its Reduction . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
Meteors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 The Sources of Noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
Zodiacal Light . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Photosite Size and Image Quality . . . . . . . . . . . . . . . . . . 54
Polar Auroras . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Improving the Signal-to-Noise Ratio . . . . . . . . . . . . 55
Lunar and Solar Eclipses . . . . . . . . . . . . . . . . . . . . . . . . 15 Compositing Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
Artificial Satellites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Compositing by Sum and Median . . . . . . . . . . . . . . 55
Processing and Touch-Ups . . . . . . . . . . . . . . . . . . . . . . . . . 19 Reduction of Noise on a Single Image . . . . . . . . . . . . . . 58
Creating Panoramas and Mosaics . . . . . . . . . . . . . . 20 Advice for Image Calibration . . . . . . . . . . . . . . . . . . . . . . 58
Making Time-Lapse Movies . . . . . . . . . . . . . . . . . . . . . 21
Chapter 4
Chapter 2 Using Your Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
Cameras for Astrophotography . . . . . . . . . . . . . . . . . . . 25 Attaching the Camera to the Telescope . . . . . . . . . . . . 63
The Sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 Piggyback Attachment . . . . . . . . . . . . . . . . . . . . . . . . . 63
Sensor Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 Prime Focus Attachment . . . . . . . . . . . . . . . . . . . . . . . 63
Image Acquisition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 Increasing the Focal Length . . . . . . . . . . . . . . . . . . . . . 64
Exposure Phase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 Use of Focal Reducers . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
Reading and Digitization Phase . . . . . . . . . . . . . . . . . 28 Afocal Attachments . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
Quantum Efficiency and Spectral Sensitivity . . . 29 Attaching a Photographic Lens to a Camera . . . . 68
Color Sensors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 Calculating the Field and Pixel Resolution . . . . . . . . . 69
Types of Cameras . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 Calculating the Field of an Image . . . . . . . . . . . . . . . 69
CCD Cameras . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 Calculating the Sampling and Size of Objects . . . 71
Consumer Digital Cameras . . . . . . . . . . . . . . . . . . . . . 35 Telescope Collimation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
Astronomical Video Cameras . . . . . . . . . . . . . . . . . . . 36 Tips for a Good Collimation . . . . . . . . . . . . . . . . . . . . . 72
Computers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 What Adjustment for What Telescope? . . . . . . . . . 72
Focusing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
Focusing Tolerances . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
Focusing Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
Tips and Tricks for Good Focusing . . . . . . . . . . . . . . 75
vi
TABLE OF CONTENTS
Chapter 5 The Sun in Hα . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122
The Planets and the Moon . . . . . . . . . . . . . . . . . . . . . . . . 79 The Hα Interference Filter . . . . . . . . . . . . . . . . . . . . . . 124
Telescopes and Resolution . . . . . . . . . . . . . . . . . . . . . . . . . 80 The Calcium K Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127
What Are the Limits of Resolution? . . . . . . . . . . . . . 81 Cameras, Imaging, and Processing . . . . . . . . . . . . . . 127
Telescopes for Planetary Imaging . . . . . . . . . . . . . . . 82 Solar Eclipses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130
Chromatic Aberration . . . . . . . . . . . . . . . . . . . . . . . . . . 82 Solar Transits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133
The Effect of a Central Obstruction . . . . . . . . . . . . . 83 The Characteristics of a Solar Transit . . . . . . . . . . . . . . 133
Collimation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 Equipment and Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . 135
Mounts and Tracking . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
The Atmosphere . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 Chapter 7
Cameras and Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88 Imaging Deep-Sky Objects . . . . . . . . . . . . . . . . . . . . . . . . 139
Focal Length and Sampling . . . . . . . . . . . . . . . . . . . . . 91 Telescopes for Deep-Sky Photography . . . . . . . . . . . . . 140
Image Capture at the Telescope . . . . . . . . . . . . . . . . . 92 Focal Length and Focal Ratio . . . . . . . . . . . . . . . . . . . . 141
Processing the Images . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93 Field Coverage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142
Select and Stack the Best Images . . . . . . . . . . . . . . . 93 Collimation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148
Calibrating, Registering, and Combining Mounts for Deep-Sky Imaging . . . . . . . . . . . . . . . . . . . . . 149
Images . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96 Fixed Mounts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149
Enhancement of Details . . . . . . . . . . . . . . . . . . . . . . . . 96 Motorized Alt-Az Mounts . . . . . . . . . . . . . . . . . . . . . . . 149
Color Adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98 Motorized Equatorial Mounts . . . . . . . . . . . . . . . . . . 150
Animations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98 Polar Alignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152
Stereo Images . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99 Using a Polar Finder . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154
The Purpose of Image Processing . . . . . . . . . . . . . . . 100 Computerized Polar Alignment . . . . . . . . . . . . . . . . . 155
The Planets and Their Satellites . . . . . . . . . . . . . . . . . . . 101 Alignment with the Telescope Finder . . . . . . . . . . . 155
Mercury . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101 Refining the Polar Alignment . . . . . . . . . . . . . . . . . . . 155
Venus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102 Tracking Errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157
Mars . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102 Periodic Drive Errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157
Jupiter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104 The Other Tracking Errors . . . . . . . . . . . . . . . . . . . . . . 158
Saturn . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104 Guiding the Exposure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158
Uranus and Neptune . . . . . . . . . . . . . . . . . . . . . . . . . . . 105 Parallel Guiding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159
The Satellites of the Planets . . . . . . . . . . . . . . . . . . . . 105 Off-Axis Guiding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159
Photography of the Moon . . . . . . . . . . . . . . . . . . . . . . . . . 106 Deep-Sky Objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164
Lunar Close-Ups . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106 Stars . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164
The Peculiar Movement of the Moon . . . . . . . . . . . 107 Diffuse Nebulae . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165
Photographing the Whole Lunar Disk . . . . . . . . . . . 107 Planetary Nebulae . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167
The Earthshine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109 Galaxies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168
Lunar Eclipses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109 Comets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170
Lunar Occultations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111 Asteroids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172
The ISS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112 The Atmosphere . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173
Color, Black and White, and Filters . . . . . . . . . . . . . . . . . 174
Chapter 6 Broadband Filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174
The Sun . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117 Narrowband Filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177
The Sun in Broadband Light . . . . . . . . . . . . . . . . . . . . . . . 118 Light-Pollution Filters . . . . . . . . . . . . . . . . . . . . . . . . . . 178
Using Broadband Filters . . . . . . . . . . . . . . . . . . . . . . . . 118 DSLRs: Infrared-Blocking Filters and H-Alpha . . . 179
Cameras, Imaging, and Processing . . . . . . . . . . . . . . 121 Selecting and Setting the Camera . . . . . . . . . . . . . . . . . . 180
DSLR or CCD Camera? . . . . . . . . . . . . . . . . . . . . . . . . . . . 181
What Exposure Time? . . . . . . . . . . . . . . . . . . . . . . . . . . 181
The Other Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183
vii
TABLE OF CONTENTS
Finding Objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184 Appendix 5:
Centering with a Finder . . . . . . . . . . . . . . . . . . . . . . . . 184 Checking and Adjusting an Equatorial Mount . . . . . 216
Imaging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185 Measuring the Periodic Error . . . . . . . . . . . . . . . . . . . 216
Preparing for the Imaging Session . . . . . . . . . . . . . . 185 Adjusting the Mount . . . . . . . . . . . . . . . . . . . . . . . . . . . 216
The Dithering Technique . . . . . . . . . . . . . . . . . . . . . . . 187 Appendix 6:
Processing the Images . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188 Making Eclipse Sequences . . . . . . . . . . . . . . . . . . . . . . . . . 218
Gradient Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190 Preparing for Imaging . . . . . . . . . . . . . . . . . . . . . . . . . . 218
Levels and Curves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191 Assembling the Frames . . . . . . . . . . . . . . . . . . . . . . . . . 218
Improving Sharpness . . . . . . . . . . . . . . . . . . . . . . . . . . . 192
Appendix 7:
Noise Reduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193
Optimizing the Camera Settings . . . . . . . . . . . . . . . . . . . 220
Cosmetic Touch-Up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194
Optimum Individual Exposure Duration for
Mosaics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194
Deep-Sky Imaging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220
Color Processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195
Optimal DSLR Deep-Sky ISO Setting . . . . . . . . . . . . 221
Processing the Colors of Stars and Galaxies
White Balance Coefficients Applicable to
Photographed with a Color Sensor . . . . . . . . . . . . . . 196
DSLR (RAW) and RGB Imaging . . . . . . . . . . . . . . . . . . 222
Processing the Colors of Stars and Galaxies
Appendix 8:
Photographed with a Monochrome Sensor
Meteor Showers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222
and LRGB Filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196
Processing the Colors of Emission Nebulae
Photographed with a Color Sensor . . . . . . . . . . . . . . 198
Processing the Colors of Emission Nebulae
Photographed with a Monochrome Sensor
Using RGB or Narrowband Filters . . . . . . . . . . . . . . . 198
Appendices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205
Appendix 1:
File Formats and Operations . . . . . . . . . . . . . . . . . . . . . . . 205
Common File Formats . . . . . . . . . . . . . . . . . . . . . . . . . . 205
Displaying Images . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207
Common Operations on Images . . . . . . . . . . . . . . . . 207
Appendix 2:
Astronomical Cameras and Software . . . . . . . . . . . . . . 208
Video and CCD Cameras . . . . . . . . . . . . . . . . . . . . . . . . 208
Filters and Photographic Accessories . . . . . . . . . . . 209
Astronomical Software . . . . . . . . . . . . . . . . . . . . . . . . . 210
Appendix 3:
From the Sensor to the Image . . . . . . . . . . . . . . . . . . . . . 210
Readout of the Image . . . . . . . . . . . . . . . . . . . . . . . . . . . 210
Obtaining a Color Image . . . . . . . . . . . . . . . . . . . . . . . . 210
Black-and-White Mode with a Color Camera . . . . 212
Appendix 4:
Uniformity Defects—Causes and Remedies . . . . . . . 212
Vignetting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213
Dust . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215
viii
FOREWORD
Foreword
Look upward on a hot summer night. The stars are right
there, at your fingertips, just waiting to be photographed.
Find a spot away from the city lights, set up your camera
on a tripod, adjust the zoom to the wide-angle position,
choose a constellation, or just aim randomly toward the
Milky Way. Focus manually, and start a 20-second expo-
sure. Congratulations, you just captured your first astro-
nomical photograph! If you enjoyed the challenge and
want to go further, this book is written for you. It is also
for those who are disappointed in their results and want
to learn how to improve.
The book you are holding in your hand contains most of
what I experienced and learned over a period of more than
20 years using telescopes, digital cameras, CCD cameras,
video cameras, and software of all kinds. After deciding
that the advent of digital sensors marked the beginning
of a new era in amateur astronomy, I bought my first CCD
camera in 1993. It is with the same enthusiasm that I con-
tinue to photograph the night sky in all its facets today.
One can say that the digital revolution has kept its promise:
the results achieved by many amateurs today exceed the
best results of the greatest observatories a generation ago.
Do not be intimidated by the number of pages in this
book. It is due to the scope of the topic and the wide vari-
ety of celestial objects available to photograph. You cannot
photograph a galaxy in the same manner that you would
a planet or an eclipse. Focal lengths used to photograph
the entire celestial sphere (page 9) and Saturn (page 80)
differ by a factor of more than a thousand! In addition, a
wide variety of imaging equipment is now available, and
it is necessary to discuss all the types of gear commonly
used in astrophotography. For example, the explanation
in chapter 5 about the advantages and disadvantages of
refractors doesn’t apply to you if you own a Newtonian
telescope—unless you decide, after reading these pages,
to change your setup!
I designed this book to make it as complete and self-
sufficient as possible. However, this is not a course in
Astrophotography can also be practiced in broad daylight, and even in the presence of
digital photography, computers, or general astronomy,
clouds, as was the case for this close approach of the moon and Venus on June 18, 2007
and reading some additional resources about those sub-
jects may therefore be useful. Anyway, you do not need
to be a computer whiz or an optical scientist to capture
ix