Patrick Moore's Practical Astronomy Series

Springer-Verlag London Ltd.

Other titles in this series

The Observational Amateur Astronomer Patrick Moore (Ed.)

Telescopes and Techniques C.R. Kitchin

The Art and Science of CCD Astronomy David Ratledge (Ed.)

The Observer's Year Patrick Moore

Seeing Stars Chris Kitchin and Robert W. Forrest

Photo-guide to the Constellations Chris Kitchin

The Sun in Eclipse Michael Maunder and Patrick Moore

Software and Data for Practical Astronomers David Ratledge

Amateur Telescope Making Stephen F. Tonkin

Observing Meteors, Comets, Supernovae and other Transient Phenomena Neil Bone

Astronomical Equipment for Amateurs Martin Mobberley

Transit: When Planets Cross the Sun Michael Maunder and Patrick Moore

Practical Astrophotography Jeffrey R. Charles

AstroFAQs Stephen F. Tonkin

Deep-Sky Observing Steven R. Coe

The Deep-Sky Observer's Year Grant Privett and Paul Parsons

Peter T. Wlasuk

With 86 Figures

Springer

Additional material to this book can be downloaded from http://extras.springer.com

Peter T. Wlasuk, FRAS Department ofPhysics and Astronomy, Florida International University, UP Campus, Miami, Florida 33185, USA

Dedicated to Patrick Moore, who has inspired the author and countless others to observe and study the Moon

Patrick Moore's Practica1 Astronomy Series ISSN 1431-9756

British Library Cataloguing in Publication Data Wlasuk, Peter

Observing the moon. - (Practical astronomy) 1. Moon - Observers' manuals I. Title 523.3

ISBN 978-1-4471-1152-8 ISBN 978-1-4471-0483-4 (eBook) DOI 1O.1007/978-1-4471-0483-4

Library of Congress Cataloging-in-Publication Data Wlasuk, Peter, 1962-

Observing the moon / Peter T. Wlasuk. p. cm - (Practical astronomy, ISSN 1431-9756) ISBN 978-1-4471-1152-8

1. Moon-Observers' manuals. I. Title. II. Series. QB581.W632000 523.3-dc21 00-033820

Apart from any fair dealing for the purposes of research or private study, or criticism or review, as permitted under the Copyright, Designs and Patents Act 1988, this publication may only be reproduced, stored or transmitted, in any form or by any means, with the prior permis sion in writing of the publishers, or in the case of reprographic reproduction in accordance with the terms of licences issued by the Copyright Licensing Agency. Enquiries concerning reproduction outside those terms should be sent to the publishers.

© Springer-Verlag London 2000 Originally published by Springer-Verlag London Berlin Heidelberg in 2000 Softcover reprint of the hardcover lst edition 2000

The use of registered names, trademarks etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant laws and regulations and therefore free for general use.

The publisher makes no representation, express or implied, with regard to the accuracy of the information contained in this book and cannot accept any legal responsibility or liability for any errors or omissions that may bemade.

Typeset by EXPO Holdings, Malaysia

58/3830-543210 Printed on acid-free paper SPIN 10739180

Preface

Why write another guide to observing the Moon? That was the question I was pondering as I began this project, having a fine collection of "classic" lunar guidebooks dating back to 1791 in my own library. As a Fellow of the Royal Astronomical Society (RAS), member of the American Astronomical Society's Division for Planetary Sciences (AAS DPS), and member of the American Geophysical Union (AGU), I am fortunate to know many pro­fessionallunar scientists who keep me up to date with developments in lunar science -contrary to public perception, lunar science has definitely not stagnated since the last Apollo, No. 17, left the surface of the Moon in December, 1972. I am also lucky to know many amateur lunar observers, who, like me, enjoy actually looking at the Moon with tele­scopes and imaging it with a wide variety of devices ranging from regular 35 mm cameras to video recorders and CCD cameras. My friends who study the Moon, whether in their professions or just for fun, gave me several reasons for doing "another" lunar guidebook.

First, the last lunar observer's guide of any length was published over ten years ago, and many reviewers noted that it was badly out of date even then. It contained little discussion of modern lunar geology, much less what we learned from the exploration of the Moon by spacecraft, or from the Apollo astronauts and the many scientists who studied the lunar rocks and soil they brought back to Earth. Two shorter works have appeared in recent years, both written by amateur astronomers, that, much to their credit, finally begin to discuss these exciting discoveries, but one of these is privately published and not widely available. I am not surprised that this is the case, for neither NASA nor lunar scientists went out of their way to explain breakthroughs in our understanding of the Moon's geology or origin. Even the late Carl Sagan, whom I greatly admired for his grasp of how important it is for scientists to excite the tax-paying public about the worthy work they do, called the Moon "boring"!

As a result, very few lay persons, even those who are interested in astronomy, can tell me what we have learned about the Moon since World War II, when the impact theory finally overtook the theory of lunar volcanoes, or "lunavoes" as the late Axel Firsoff color­fully called them, to explain the formation of the majority oflunar craters. I suspect that if Apollo were in full swing today, the public would be better informed, both because the science community is now far more skilled at public relations than it was in the early 1970s, and because of the Internet and other technological wonders that allow the public to access and share information that was unavailable only a short time ago.

A second reason for writing an updated guide to observing the Moon is really a whole set of reasons. Since the last guidebooks were published, the evolution of the personal computer (PC) and the emergence of video and CCD imaging technologies have brought to the amateur new techniques not even dreamt of back in the early 1970s, when I started to observe the Moon for myself. Compare the CCD images of the Moon shown in Chapter 12 with photographs of the same lunar surface features taken by the Lunar Orbiter space­craft, long considered the "ultimate" lunar images, and you will see just how far amateur lunar observing and imaging have advanced. Presenting this excellent work, which so richly deserves an audience, is another good reason for writing a new lunar guidebook, and I hope that seeing what can be done will inspire others to take up lunar observing with a new enthusiasm. That is why I chose to include a lunar atlas (on the CD-ROM) produced by an amateur lunar imager, rather than just republishing NASA spacecraft photos that

vi Observing the Moon

bear little resemblance to what the user of this handbook is likely to see in their own telescope.

A third reason for writing a new guide to the Moon is to correct the huge number of errors that plague the classic guidebooks. When I first started observing the Moon over twenty-five years ago, I thought there was something seriously wrong with my eyes, or perhaps it was my telescope - I simply could not see many of the details that the authors of those classic guidebooks told me I was supposed to see! In time, as my observing skills and confidence improved, I realized that the fault was not with my eyes or my telescope -the classic guidebooks, in their descriptions of lunar surface features, contain literally hundreds of errors. When I was employed at the Yale University Department of Astronomy in the 1980s, I had the privilege of working under the tutelage of Dorrit Hoffleit on the Yale Bright Star Catalogue and its Supplement, as well as the Yale Catalogue of Trigonometric Parallaxes.

From this cataloging work I learned how to find and correct errors, and resolved to apply what I had learned to correcting errors in the descriptions of lunar surface features. Professional lunar scientists may think it silly to worry about such things, but it is not -amateur lunar observers have long enjoyed knowing what to "look for" on the face of the Moon, and they are entitled to an accurate guidebook. For the past quarter-century I have observed the Moon through a wide variety of instruments, ranging from a fine 60 mm Japanese refractor made in the late 1950s to the giant 40-inch (I-meter) refractor at the University of Chicago's Yerkes Observatory in Williams Bay, Wisconsin. My principal instruments for observing the Moon today include a classic Celestron 10 f113.5 Schmidt-Cassegrain from 1969, the year that Neil Armstrong took those first famous steps on the lunar soil, and two antique reflectors made by the English pioneer telescope­makers George Calver and George With.

The heart of this book is comprised by Chapters 4 to 7, which contain detailed descrip­tions oflunar surface features. As I observed each of these features over the years, I would be careful not to study any photographs of those features from spacecraft, lest I got some preconceived idea of what I was "supposed" to see. I did refer to the classic lunar guide­books available to me, but with a critical eye - I learned not to assume that they were correct. After making careful notes and drawings of the features, I would next consult Lunar Orbiter or other high-resolution images of the features, to verify what I had observed, finally comparing both the photographic image and my description to the descriptions in the classic guidebooks.

I discovered that the authors of the classic guidebooks often copied their descriptions from one another, which resulted in the propagation of innumerable mistakes. If you read the scientific literature from the time these guidebooks were written, it is clear that there was an intense contest among the classic observers to outdo one another to "discover" and to be the first to report subtle "new" details oflunar topography. This competition led, I believe, to observers pushing their instruments and their eyes beyond what could be reli­ably observed or recorded. Occasionally, strange beliefs in lunar vegetation or active lunar volcanism undoubtedly influenced what observers saw, or thought they saw. It was once quite fashionable to report dark radial bands spiraling across many lunar craters, as well as vivid but ephemeral colors in lunar features that we now know to be inconsistent with the make-up oflunar rocks and soil as discovered by examining them at first hand in our geologic laboratories.

A fourth objective in writing this book combines two of the others - I wanted to relate what we have learned about lunar geology in the past fifty years to the descriptions of lunar surface features, so that amateur lunar observers can get more out of their observing sessions. As majestic as the Moon is through a telescope, it can quickly get boring to look at one crater after another with no understanding of how they formed, how they differ from other craters or other lunar surface features, or whether a particular crater (or other formation) raises any questions that baffle even today's professional lunar scientists.

The amateur lunar observer who understands at least a modicum of lunar geology and geologic history will not get bored with the Moon, ever, as there are always new mysteries

Preface vii

to be unraveled. Today, many amateur lunar observers are discussing sophisticated prob­lems oflunar geology, asking well-phrased questions about the Moon's topography and how it got that way. Many are contributing valuable data to lunar studies in areas such as lunar occultations.

There are many more reasons for a book like this one, but rather than list them all, I would like to finish by acknowledging just a few of the many persons who contributed to this work, by providing text or illustrations, or helpful advice: Sally Beaumont; Julius Benton; Bill Davis; Bill Dembowski; Maurizio Di Sciullo; Eric Douglass; Colin Ebdon; Harry Jamieson; Anthony Kinder, Librarian, British Astronomical Association; Joe LaVigne; Robert Levitt; Mary A. Noel, Lunar and Planetary Institute (LPI), Houston, Texas; Michael Oates; Bernard Wahl; John Westfall; Ewen Whitaker, Lunar and Planetary Laboratory, University of Arizona; Ted Wolfe; and the Lunar Sections of the Association of Lunar and Planetary Observers and of the British Astronomical Association. Unless indicated otherwise, these persons are all amateur lunar observers, and without their fine work this book would not have been possible. If I have forgotten to thank anyone, which is very possible given the many persons with whom I discuss the Moon, I apologize. I also wish to thank my wife Patty, for helping with the proofreading and illustrations, and for her encouragement. I hope you enjoy this book!

Peter T. Wlasuk, FRAS

Contents

1 Introduction to the Moon .. Vital Statistics . . . ..... . The Moon's Motions in Space Lunar Librations and Eclipses

2 The Basic Kinds of Lunar Formations The Lunar Craters The Lunar Maria and Bays The Lunar Rilles The Lunar Mountains

3 A Crash Course in Lunar Geology . Lunar Geology - What Have We Learned? A Lunar Geologist's Lexicon ..... . Our Changing Views of Lunar Geology How the Moon Came to Be The Lunar Geologic Timescale Lunar Geology's Unsolved Mysteries

4 Lunar Features - Northeast Quadrant

5 Lunar Features - Southeast Quadrant

6 Lunar Features - Northwest Quadrant

7 Lunar Features - Southwest Quadrant

8 Introduction to Observing the Moon . Why Observe the Moon? . . . . . . .. Choosing a Telescope for Lunar Observing Finding Your Way Around the Moon Eyepieces and Filters . .

9 Drawing Lunar Features Getting Started ... . Questions to Ask ... . Some Important Data What to Do with Your Drawings

10 Lunar Topographic Studies The Selected Areas Program . Lunar Transient Phenomena

1 1

4

8

13 13 19

22 23

27

27

28 31

32

33

36

39

55

71

87

105 105 107

110 111

115 115 118 120 123

125 125 133

x Observing the Moon

11 Lunar Eclipses and Occultations Lunar Eclipses Lunar Occultations

12 Imaging the Moon Photographing the Moon with Telephoto Lenses (Michael Oates) Lunar Photography: An Apogee-Perigee Project (Bill Dembowski) Vertical Studies (Bill Dembowski) ............... . Imaging the Moon with an Astro-Video Camera (Joe LaVigne) The CD-ROM Lunar Atlas ........ . Lunar CCD Imaging (Maurizio Di Sciullo)

Glossary of Lunar Terminology

Further Reading . . . .

Lunar Observing Forms

Index .......... .

Files and Lunar Atlas on the CD-ROM

Instructions for Using the CD-ROM .

137

137

141

145 146 149 150 152 159 160

166

168

170

177

180

182