Choosing and Using a New CAT: Getting the Most from Your Schmidt Cassegrain or Any Catadioptric Telescope

334 Pages·2009·89.98 MB·English

by  Rod Mollise (auth.)

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
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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: Y ou
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) l ooks 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, though. What also sets these
CATs apart is their versatility. Other telescope types—Dobsonian reflectors and
apochromatic refractors, for example—may do some things better than the SCT,