Binoculars and Scopes

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Binoculars and Scopes

Field Guide to

Paul R. Yoder, Jr.

Daniel Vukobratovich

SPIE Field Guides Volume FG19

John E. Greivenkamp, Series Editor

Bellingham, Washington USA

Downloaded From: https://www.spiedigitallibrary.org/ebooks/ on 22 Oct 2021 Terms of Use: https://www.spiedigitallibrary.org/terms-of-use

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Library of Congress Cataloging-in-Publication Data

Yoder, Paul R.

Field guide to binoculars and scopes / Paul R. Yoder and Daniel Vukobratovich.

p. cm. – (The field guide series ; FG19) Includes bibliographical references and index.

ISBN 978-0-8194-8649-3

1. Binoculars. 2. Telescopes. I. Vukobratovich, Daniel. II. Title.

QC373.B55Y63 2011 681⁰.412–dc22

2011009994 Published by

SPIE P.O. Box 10

Bellingham, Washington 98227-0010 USA Phone: +1.360. 676.3290

Fax: +1.360.647.1445 Email: [email protected] Web: http://spie.org

The content of this book reflects the work and thought of the author. Every effort has been made to publish reliable and ac- curate information herein, but the publisher is not responsible for the validity of the information or for any outcomes resulting from reliance thereon.

First printing

Printed in the United States of America.

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Introduction to the Series

Welcome to the SPIE Field Guides—a series of publications written directly for the practicing engineer or scientist.

Many textbooks and professional reference books cover optical principles and techniques in depth. The aim of the SPIE Field Guides is to distill this information, providing readers with a handy desk or briefcase reference that provides basic, essential information about optical principles, techniques, or phenomena, including definitions and descriptions, key equations, illustrations, application examples, design considerations, and additional resources. A significant effort will be made to provide a consistent notation and style between volumes in the series.

Each SPIE Field Guide addresses a major field of optical science and technology. The concept of these Field Guides is a format-intensive presentation based on figures and equations supplemented by concise explanations. In most cases, this modular approach places a single topic on a page, and provides full coverage of that topic on that page. Highlights, insights, and rules of thumb are displayed in sidebars to the main text. The appendices at the end of each Field Guide provide additional information such as related material outside the main scope of the volume, key mathematical relationships, and alternative methods. While complete in their coverage, the concise presentation may not be appropriate for those new to the field.

The SPIE Field Guides are intended to be living documents.

The modular page-based presentation format allows them to be easily updated and expanded. We are interested in your suggestions for new Field Guide topics as well as what material should be added to an individual volume to make these Field Guides more useful to you. Please contact us at [email protected].

John E. Greivenkamp, Series Editor College of Optical Sciences The University of Arizona

Field Guide to Binoculars and Scopes

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The Field Guide Series

Field Guide to Geometrical Optics, John E. Greivenkamp (FG01)

Field Guide to Atmospheric Optics, Larry C. Andrews (FG02) Field Guide to Adaptive Optics, Robert K. Tyson & Benjamin W.

Frazier (FG03)

Field Guide to Visual and Ophthalmic Optics, Jim Schwiegerling (FG04)

Field Guide to Polarization, Edward Collett (FG05) Field Guide to Optical Lithography, Chris A. Mack (FG06) Field Guide to Optical Thin Films, Ronald R. Willey (FG07) Field Guide to Spectroscopy, David W. Ball (FG08)

Field Guide to Infrared Systems, Arnold Daniels (FG09) Field Guide to Interferometric Optical Testing, Eric P. Goodwin

& James C. Wyant (FG10)

Field Guide to Illumination, Angelo V. Arecchi; Tahar Messadi;

R. John Koshel (FG11)

Field Guide to Lasers, Rüdiger Paschotta (FG12) Field Guide to Microscopy, Tomasz S. Tkaczyk (FG13)

Field Guide to Laser Pulse Generation, Rüdiger Paschotta (FG14)

Field Guide to Infrared Systems, Detectors, and FPAs, Second Edition, Arnold Daniels (FG15)

Field Guide to Laser Fiber Technology, Rüdiger Paschotta (FG16)

Field Guide to Wave Optics, Dan Smith (FG17)

Field Guide to Special Functions for Engineers, Larry C.

Andrews (FG18)

Field Guide to Binoculars and Scopes, Paul R. Yoder, Jr. &

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The intent of this Field Guide is to explain the functions and configurations of various types of binoculars and scopes to the beginner as well as to the experienced user. We also attempt to show why a given instrument is designed the way it is.

Binoculars of various sizes—ranging from pocket size to giant models, high magnification and wide angle types, and ones used for military, law enforcement, marine and amateur astronomical applications—are considered. Scopes include small monoculars, spotting scopes, riflescopes, weapon sights, and astronomical types as large as 300 mm. Mounts for the larger instruments are also considered. Theoretical explanations of optical and mechanical systems performance are summarized.

We acknowledge with thanks Bushnell Outdoor Products, Carl Zeiss AG, Carl Zeiss Sport Optics, Leuopold & Stevens, Möller-Wedel GmbH, Questar, Schultz Loupe Direct, Steiner, Swarovski Optik KG, and the University of Arizona’s College of Optical Sciences for technical information and illustrations included here.

We also thank John Greivenkamp, Wright Scidmore, and Bruce Walker for reviewing the manuscript and offering valuable suggestions for corrections and clarifications.

Any mention of specific hardware in this Field Guide is not meant to be an endorsement, but rather, it is intended to cite an example of a certain instrument configuration or design feature of potential interest to the reader.

The authors dedicate this Field Guide with love to the memory of Paul’s late wife, Betty, and to Daniel’s wife, Suzanne.

Paul R. Yoder, Jr. Daniel Vukobratovich

Norwalk, Connecticut Tucson, Arizona

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vi

Table of Contents

Glossary ix

Fundamentals 1

What Are Binoculars and Scopes? 1

How Are These Instruments Used? 2

Basic Optical System Parameters 3

Instrument Size and Weight 5

Pertinent Eye Parameters 6

Structure of the Eye 6

Pupil Size 7

Interpupillary Distance 9

Resolving Power 10

Accommodation 12

Stereoscopic Capability 13

Luminosity and Chromatic Sensitivities 14

Basic Configurations 15

Galilean Systems 15

Keplerian Systems 17

Binoculars 19

Binocular Types—General Considerations 19

Compact Binoculars 20

Mid-Size Binoculars 21

Full-Size Binoculars 22

Giant Mounted Binoculars 23

High-Magnification and Wide-Angle Binoculars 24 Military and Law Enforcement Binoculars 25

Astronomical Binoculars 27

Monoculars and Spotting Scopes 29

Monoculars 29

Spotting Scopes 30

Riflescopes and Weapon Sights 32

Riflescopes 32

Weapon Sights 34

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vii Table of Contents

Astronomical Scopes 35

Refracting Form 35

Newtonian, Cassegrain, and Gregorian Forms 36 Schmidt–Cassegrain and Schmidt–Gregorian Forms 37

Maksutov–Cassegrain Form 38

Richest-Field Form 39

Mounts for Astronomical Binoculars and Scopes 40

Light-Duty Mounts 40

Heavy-Duty Mounts 41

Tripod Attributes 43

More about Equatorial Mounts 44

Dobsonian Mounts 46

GOTO Drives 47

Binocular and Scope Performance 48 Stereoscopic Vision through a Binocular 48

Resolving Power with Optics 49

Binocular/Scope Efficiency 51

Handheld-Binocular Efficiency 53

Distortion Effects 54

Limiting Magnitude of a Binocular or Scope 55

Diffraction Effects 57

Obscuration Effects 58

Atmospheric Scatter Effects 59

Atmospheric Seeing Effects (Elevated Path) 60 Atmospheric Seeing (Horizontal Path) 61

Optical System Considerations 62

Focusing for Different Target Locations 62

The Diopter Adjustment 64

Erecting Prisms 65

Prism Refractive-Index Effects 67

Lens Erecting Systems 69

Eyepiece Configurations 70

Selection of Interchangeable Eyepieces 72

The Field Stop 74

Parallax 75

Light Transmission 76

Vignetting 78

Stray Light 79

Light Baffles 80

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viii

Table of Contents

Reticles 82

Variable-Magnification (Zoom) Systems 83

Image Stabilization Techniques 85

Rangefinding Techniques 87

Mechanical System Considerations 88

Overall Size of a Binocular 88

Weight of a Binocular 90

Ergonomics 92

Environmental Considerations 94

Housing Design 95

Binocular Hinge Mechanisms 96

Binocular Collimation Mechanisms 97

Object Focus Mechanisms 99

Diopter Adjustment Mechanisms 100

Sealing and Purging 101

Photography through Binoculars and Scopes 103

Basic Photography Techniques 103

Interfacing the Camera 105

Integral Cameras 107

Maintenance of Binoculars and Scopes 109 Protection and Cleaning of the Instrument 109

Testing the Instrument 110

Test Setups and Methods 111

Modular Construction 114

Desirable Instrument Attributes 116

General Considerations 116

Attributes for Bird-Watching Binoculars 117 Attributes for Hunting Binoculars 118 Attributes for Military Binoculars 119 Attributes for Astronomical Binoculars 120

Attributes for Spotting Scopes 121

Attributes for Astronomical Refractor Scopes 122

Attributes for Newtonian Scopes 123

Attributes for Catadioptric Scopes 124

Equation Summary 125

Bibliography 128

Index 135

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ix Glossary of Symbols

A Age, distance, prism face width

A/R Antireflection (coating)

AFOV Apparent field of view

AIM Aerial image modulation

AS Aperture stop

B Stereo baseline

BFD Back focal distance

CCD Charge-coupled device

cd Candela

CF Center focus

CED Clear eye distance

C²_n Index of refraction structure

D Diopter (unit)

DEP Diameter of entrance pupil

D_{EY E} Diameter of eye pupil

DF S Diameter of field stop

D_OBS Diameter of obscuration

DX P Diameter of exit pupil

e Naperian logarithm base

E Elastic modulus, efficiency

EFL Effective focal length

EP Entrance pupil

ER Eye relief

f_EP EFL of eyepiece

fOBJ EFL of objective

f_n Fundamental vibrational frequency

f /number Relative aperture

FOV Field of view

GEM German equatorial mount

GOTO Go to (drive; mount)

I Moment of inertia

IC Critical angle of incidence

IF Internal focus

IP Inverted Porro

IPD Interpupillary distance

L Distance, luminance level

LCD Liquid crystal display

LED Light-emitting diode

LOS Line of sight

lp Line pair

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x

Glossary of Symbols

M Magnification

MgF₂ Magnesium fluoride (A/R coating) ML Limiting magnitude

M_V Apparent visual magnitude mil US military angular unit

MLD Multilayer dielectric (A/R coating) MTF Modulation transfer function n Refractive index

NIR Near infrared

O Axis offset

R_{EY E} Resolution of eye; detection range of eye RFOV Real field of view

R_{OP T} Resolution of the eye through a optical instrument, detection range of the eye through an optical instrument

RFT Richest-field telescope r₀ Fried parameter

R_{OP T} Resolution with optics; detection range with optics R_V Visual range

S Distance, Strehl ratio

S_{OE A} Strehl ratio due to obscuration t Axial path length, time

T Temperature, light transmission TIR Total internal reflection

Ts Settling time

XP Exit pupil

XPD Exit pupil distance V_{EY E} Visual acuity of eye V_{OP T} Visual acuity with optics VTR Vapor transmission rate W Mass flow of water

α 1/2 real field of view in object space β 1/2 apparent field of view in image space

∆ Difference between parameters; eyepiece focus motion per diopter

ε Ratio of obscuration diameter to D_EP η Damping coefficient

θ Angle designation

λ Wavelength