Patrick Moore’s Practical Astronomy Series For other titles published in the series, go to www.springer.com/series/3192 Hunting and Imaging Comets Martin Mobberley Martin Mobberley Denmara Cross Green Cockfield Bury St. Edmunds, Suffolk IP30 0LQ United Kingdom ISSN 1431-9756 ISBN 978-1-4419-6904-0 e-ISBN 978-1-4419-6905-7 DOI 10.1007/978-1-4419-6905-7 Library of Congress Control Number: 2010937433 © Springer Science+Business Media, LLC 2011 All rights reserved. This work may not be translated or copied in whole or in part without the written permission of the publisher (Springer Science+Business Media, LLC, 233 Spring Street, New York, NY 10013, USA), except for brief excerpts in connection with reviews or scholarly analysis. Use in connection with any form of information storage and retrieval, electronic adaptation, computer software, or by simi- lar or dissimilar methodology now known or hereafter developed is forbidden. The use in this publication of trade names, trademarks, service marks, and similar terms, even if they are not identified as such, is not to be taken as an expression of opinion as to whether or not they are subject to proprietary rights. Printed on acid-free paper Springer is part of Springer Science+Business Media (www.springer.com) Preface The death knell of the amateur comet discoverer has been prematurely sounded many times in the last few decades and yet, in the twenty-first century, a steady stream of comets found by amateur astronomers appears in the astronomical headlines. The qualities possessed by the visual observers of yore are still required, namely infinite patience and a love of the night sky, but the technology has changed as has the ability to take great images of the new discoveries. While remorseless robotic dis- covery machines scour the sky each night from cloud free sites, seem- ingly invincible, every fighter knows that every adversary has weaknesses that can be exploited. The machines cannot patrol in twilight and they do not look for fuzzy objects, but moving dots. In addition, even sites like New Mexico have cloudy nights and every professional observatory is dependent on endless funds to keep the facilities going and the machines maintained. Comets are unpredictable things too, which helps the ama- teur patroller. The hour after a CCD patrol has swept over a twentieth magnitude fuzzy star, it may choose to turn on and brighten by several magnitudes, placing it firmly within the amateur’s grasp; alternatively a comet might brighten with a few days of full Moon when the profes- sional detection software cannot work and so the robotic patrols are idle. There are opportunities for the determined amateur everywhere. The current multi-million dollar blitz on the sky is largely as a result of US funding to detect NEOs in the inner solar system, but how long will that funding continue in these post credit-crunch times, especially if there is v vi Preface confidence that almost every object more than a few hundred meters across has been found? Anyway, even if the NEO patrols do continue unabated there is no doubt that amateurs will relish the challenge even if the competition gets tougher. Now, you may well have already decided that I am a fraud in this con- text! After all, you probably haven’t heard of comet Mobberley. There is a good reason for this: there isn’t one! In the early 1980s I spent several years and hundreds of hours sweeping for comets with a 36-cm f/5 New- tonian; I had quite a few near-misses, but they don’t count of course. With Halley returning in 1985/1986 I resolved to concentrate more on comet photography (which I had dabbled with since 1982) and so that has been my main thrust since then. I was encouraged in this regard by one of the greats of British astronomy in the twentieth century, the late Harold Ridley (1919–1995). Harold was the UK’s top comet photographer for many years and a true gentleman. He did not think much of reflectors and always took very long photographs using photographic plates or sheet film. His system comprised of a 7-inch (178-mm) f/7 triplet refrac- tor mounted alongside a very long 6-inch Cooke refractor guidescope. Harold was the master of the offset guided long exposure in which he manually guided, with his eye literally glued to the eyepiece, for 20–40 minutes, while trailing the guide star along a micrometer cross wire, at a carefully calculated rate, to allow for the comet’s motion. It was a badge of honor in those days to end up with a photograph in which the star trails were ruler straight and the comet frozen on the photograph. No-one ever produced straighter star trails than Harold Ridley! He was a perfectionist and learned his comet photography skills from the legendary wheelchair- bound Reggie Waterfield (1900–1986) and from Michael Hendrie. I always recall an amusing tale Harold told me regarding a particularly clear night in late 1985 when he had meticulously offset guided a photo- graph of the brightening comet Halley and then retired with the sealed photographic plate holder into his darkroom to develop the photograph. The night had been very clear indeed and Harold was excited at what the plate might show. The developing and fixing took place smoothly in the very dim red glow of the darkroom light and then, with the photograph fixed he turned on the main light. To his horror he saw that the photo- graphic plate was still lying on the worktop and therefore now bleached by the darkroom light! He had not developed the 4 × 5-inch glass photo- graphic plate at all, but the 4 × 5-inch ground glass focusing screen from the dismantled plate holder, which felt the same in the dark and looked the same in the dim red light. “It took me a long while to get over that” he laughed……many, many, months later! If Harold had not been such a heavy smoker he might still be alive now. However, he died just before the Preface vii Great Comets Hyakutake and Hale-Bopp came along and a few friends have suggested he arranged their arrival from behind the scenes! Memories of dedicated amateurs like Harold spur me on and so, although I no longer hunt for comets, I image them on a regular basis, still inspired by those photographic era stalwarts. The CCD toys we now have are twenty times more sensitive than any photographic plate and we are thoroughly spoiled with the options now available. It is an exciting time to be a comet imager and since the mid 1990s some incredible sights have come our way, not least Shoemaker-Levy 9 colliding with Jupiter, the splendid comets Hyakutake and Hale-Bopp and then, in 2007, comet C/2006 P1 (McNaught) and the exploding comet 17P/Holmes. Added to those amazing objects we have now seen fascinating space probe images of four cometary nuclei at close range. Whether you are a comet hunter or a comet imager I hope this book has something to inspire you to become even more engrossed in a phe- nomenon that, more than any other, used to have our ancestors staring in awe, presumably open-mouthed, at the sight of a hairy “broom star” monster in the sky. M. Mobberley Cockfield, UK Acknowledgements No book of this type, containing so many astronomical images, would be financially viable without the generosity of astronomers and profes- sional organizations that are happy for their fine images to be used for educational purposes. I am especially indebted to NASA in this regard whose images are generally copyright-free, thereby enhancing the quality of thousands of space and astronomy publications worldwide. I would also like to thank the following astronomers and scientific facilities whose images I have used and advice I have received while compiling this book: Charles Bell; Ed Beshore; Peter Birtwhistle; Reinder Bouma; John Broughton; Eric Bryssink; Bernhard Häusler; Michael Hendrie; Rik Hill; Karen Holland; Mike Holloway; Michael Jäger; Mark Kidger; Gary Kronk; Steve Larson; Terry Lovejoy; Dr Robert S. McMillan (on behalf of Spacewatch, the Lunar and Planetary Laboratory, the University of Ari- zona and NASA); Robert McNaught; Richard Miles; MIT Lincoln Labo- ratory, Lexington, Massachusetts; Gustavo Muler; Michael Oates; Prof. Greg Parker & Noel Carboni; Arnie Rosner; Juan Antonio Henríquez Santana; Ian Sharp; Clay Sherrod; Starlight Xpress; Roy Tucker. Thanks are also due to all at Springer New York and SPi for guiding this book through the production process. Finally, I thank my father Denys for his constant support in all my observing and writing projects. ix About the Author Martin Mobberley is a well-known amateur astronomer from Suffolk, England, who joined the British Astronomical Association in 1969, aged eleven, initially as a visual observer. Since the early 1980s he has been a regular photographer and imager of comets, planets, asteroids, variable stars, novae, and supernovae. He served as one of the youngest presi- dents of the British Astronomical Association, from 1997 to 1999, and in 2000 he was presented with the association’s Walter Goodacre Award. In 1997 the International Astronomical Union (IAU) named asteroid number 7239 as “Mobberley” in recognition of Martin’s contribution to amateur astronomy. Martin is the sole author of seven previous practi- cal astronomy books published by Springer as well as three children’s “Space Exploration” books published by Top That Publishing. In addi- tion he has authored hundreds of articles in the UK magazine Astronomy Now and numerous other astronomical publications, as well as appear- ing from time to time on Patrick Moore’s long-running BBC TV pro- gram The Sky at Night.