Patrick Moore’s Practical Astronomy Series For other titles published in the series, go to www.springer.com/series/3192 Choosing and Using a New CAT Getting the Most from Your Schmidt Cassegrain or Any Catadioptric Telescope Rod Mollise Rod Mollise 1207 Selma Street Mobile AL 36604 USA ISBN 978-0-387-09771-8 e-ISBN 978-0-387-09772-5 DOI: 10.1007/978-0-387-09772-5 Library of Congress Control Number: 2008934774 © Springer Science+Business Media, LLC 2009 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.com About the Author Rod Mollise is an engineer by profession. He is also the author of numerous books and magazine articles on every aspect of amateur astronomy. Known to his fans as “Uncle” Rod Mollise, he is most well known for his books about catadioptric tel- escopes (CATs), which aim to help new CAT owners get past the inexperience and anxiety that often accompanies their entry into this wonderful hobby. In addition to his books and Internet sites, Rod’s writings can frequently be found in Sky & Telescope, Night Sky Magazine, Astronomy Technology Today, and many other pub- lications. Rod also finds time to teach astronomy to undergraduates at the University of South Alabama in Mobile. When he is not on the road attending and speaking at star parties, he shares a rambling old Victorian home in Mobile’s Garden District with his wife, Dorothy, two (four-legged) cats, and, at last count, 11 telescopes. v Acknowledgements Thirty-five years of using and loving Schmidt Cassegrain telescopes (SCTs) has taught me a few things about these wonderful telescopes, but I hardly know every- thing. This book would not have been possible without the assistance of many kind and generous members of the amateur astronomy community. The input from my online catadioptric telescope (CAT) user groups proved inval- uable from start to finish. These individuals have taught me far more about SCTs than I could ever have learned on my own. Special recognition is due these out- standing amateur astronomers: Bob Berta, Cal Beard, Matthias Bopp, Paul Cezanne, Steve Clayworth, John Clothier, Richard Edelson, “Poppa Fred,” Tanveer Gani, Steve Jaynes, Andrew Johansen, Leonard Knoll, Joe Kuhn, Jim Norton, Robert Piekiel, David Polivka, R. Richins, Dick Seymour, “Doc” Clay Sherrod, Rick Thurmond, Gord Tulloch, and many more. One of the greatest things about the SCT community is the close and supportive relationship that exists between telescope users and telescope makers. The following astronomy business pros provided me with the images and software I needed to make this book a reality: Paul Rodman (AstroPlanner); Michelle Meskill (Celestron); Steve Tuma (Deepsky Astronomy Software); Paul Hobbs (Meade); Terry D’Auray, Claire Kleffel, and Peter Moreso (Imaginova/Orion Telescopes and Binoculars); John Pem- berton and all the good folks at Orion Optics UK; and Greg Crinklaw (SkyTools). Finally, as has been the case with every book I have done for Springer, three people have earned my deepest appreciation. John Watson shepherded this one along in the early days, and without his efforts it would not have been published. Pat Rochford, my best friend, checked and proofread the manuscript, and without his hard work, it would not have been much good. Dorothy Mollise, my wife and always “the brightest star in this astronomer’s sky,” contributed the most of all. Without her love and understand- ing, it would not have been written. Thanks, y’all! vii Contents About the Author ................................................................................................. v Acknowledgements .............................................................................................. vii 1 Why a CAT? ................................................................................................... 1 2 What’s a CAT? ............................................................................................... 11 3 Inside a CAT ................................................................................................. 19 4 Which CAT? .................................................................................................. 41 5 Making Friends with a CAT ........................................................................ 113 6 Accessorizing a CAT..................................................................................... 129 7 First Light With a CAT ................................................................................ 165 8 Enjoying a CAT ............................................................................................ 195 9 Care and Feeding of a CAT .......................................................................... 223 10 Computerizing a CAT .................................................................................. 237 11 Taking Pictures with a CAT ......................................................................... 259 12 Hacking a CAT .............................................................................................. 291 ix x Contents 13 Keeping the Passion Alive ........................................................................... 313 Appendix 1 Telescope and Accessory Dealers and Manufacturers .............. 319 Appendix 2 Internet Resources, Software, and Books for CAT Users .......... 323 Index ...................................................................................................................... 329 CHAPTER ONE Why a CAT? Since you’re reading this, I’m guessing you have made an exciting decision: You want a telescope. Specifically, you want a telescope for looking at the sky, a telescope that will open the depths of space to your gaze and allow you to visit the Moon, the planets, and all the strange and distant wonders of our magnificent universe. And you are not looking for just any telescope, either, but for a Schmidt Cassegrain telescope (SCT), whose full-color advertisements fill the pages of astronomy magazines. In our consumer culture, most of us have become wary of high-pressure ads from manufacturers who promise the Moon and deliver little. Luckily, that is not the case when it comes to SCTs. Sometimes, the advertising does contain hyperbole, but Schmidt Cassegrains really can deliver the Moon—and the stars, too. SCTs, like anything else, are not perfect, but when all is said and done, the Schmidt Cassegrain may be the most versatile, technologically advanced, and easy-to-use telescope ever sold to amateur astronomers. Since SCTs were first offered at prices the average person could afford way back in 1970, they have dominated the amateur astronomy telescope market. Don’t believe that? Take a stroll around the observing field of a local astronomy club during the next star party. Chances are a majority of the telescopes there will be SCTs. Fancy advertisements alone simply could not account for the enduring popularity of Schmidt Cassegrains. Something good is going on. Not that an SCT (Plate 1) looks much like a telescope of any kind to novice astronomers. Catadioptric telescopes (CATs, for short), which are telescopes that use both lenses and mirrors, do not much resemble the telescopes we are used to seeing in the movies or on television. The eyepiece is where it “ought” to be, at the end of the tube, and that tube is perched on a tripod, but that is where the similarity ends. The tube is short and fat, looking more like a beer keg than a respectable R. Mollise, Choosing and Using a New CAT, 1 DOI: 10.1007/978-0-387-09772-5_1, © Springer Science + Business Media, LLC 2009 2 Choosing and Using a New CAT Plate 1. (SCT) An 8-inch Schmidt Cassegrain tele- scope set up at a dark site and ready for an evening of deep space voyaging.” Credit: Author telescope. It is not just attached to a tripod, either. It is sitting on a complicated- looking “mount” festooned with myriad lights and switches. The SCT looks different enough in beginners’ eyes to be positively frightening, maybe scary enough to make a new astronomer who just wants a good look at the craters of the Moon turn tail and run. Appearances can deceive, however. The SCT is at heart an uncomplicated telescope. Despite its looks, its basic operation is easy to understand, and it is actually one of the most user-friendly scopes ever made. And, it is not just user friendly. A beginning amateur astronomer may start out just wanting a look at the good old Moon but will soon find the faithful SCT can take even a novice observer way beyond our cosmic neighborhood—maybe even as far as the daunting depths of the universe inhabited by the mysterious quasars. Although nothing in the design of the SCT is astoundingly innovative, its basic lay- out is extremely sound and features good optics in sizes sufficient to take even a tyro a long, long way from home. Capability is just the beginning of the SCT story,