Solar Astronomy Handbook

Description

A book by Rainer Beck, Heinz Hilbrecht, Klaus Reinsch & Peter Völker

About This Book
This book is not so much about the Sun, but about the opportunities for amateur astronomers to observe the Sun. Compared with other areas of astronomy solar observing has a number of advantages:

-Observation can be carried out during the day. You do not have to stay up all night and arrive at work the next day exhausted!
-There is an abundance of light. Unlike “Deep Sky” astronomy you actually have to discard much of the light reaching your telescope.
-You can set up your observatory in your own backyard – even in the city -there is no need to escape light pollution at remote locations.
-Observations can be made practically every clear day and some simple programs like sunspot counts can be done in just a few minutes.
-You do not need a monster telescope, even a small telescope will show an amazing amount of detail.
-The view is constantly changing, the Sun’s appearance has never been, nor will it ever be exactly the same as today.

This book was conceived and written by a group of German amateur observers. Each section was the responsibility of the amateur who had made that aspect of solar astronomy his specialty. The emphasis was on the practical and covers the kind of solar astronomy within the reach of most amateurs. Soon after publication it was declared by many reviewers as the “standard work” and much correspondence reached the authors from abroad requesting an English translation. In terms of content the basic information in the original German edition will be found here. Where necessary, updating has taken place and errors have been corrected. Numerous passages were revised taking into account the larger, inter-national circle of readers, many pictures have been added and references to German-language literature have been changed, where possible, to appropriate English-language works. The book is divided into four major parts. Part A describes instruments used in solar astronomy, offers help in making decisions with regard to buying, and provides instructions for those who might build their own instrument. Part B deals with the many different amateur observation possibilities. Part C gives encouragement and help in planning and carrying out expeditions to observe solar eclipses and gives details on observation. Part D is an extensive bibliography especially tailored for the amateur solar astronomer. Each chapter of the book is self-contained in terms of contents and the reader can turn to those subjects which interest him or her the most. Numerous cross-references are embedded within the text to point the reader to related sections.

Table of Contents

Foreword v
The Sun and Your Safety 1
Part A Instrumentation 5
A.1 Choosing a Telescope 7
A.1.1 Telescopes for White Light Observations 7
A.1.2 Observation of the Sun in Projection 7
A.1.3 Observing the Sun with Reflective Objective Filters 12
A.1.4 Observing the Sun with Eyepiece Filters 14
A.1.5 Conclusion 14
A.2 Telescope Accessories for Sun Viewing 15
A.2.1 Solar Projection Screen 15
A.2.2 Spectroscope 17
A.2.3 Micrometers 20
A.2.3.1 Graticule Eyepiece 20
A.2.3.2 Micrometer Lamella 22
A.3 Filters 25
A.3.1 Introduction 25
A.3.2 Eyepiece Filters 25
A.3.3 Objective Filters 26
A.3.4 Helioscopes 29
A.3.5 Summary 34
A.3.6 Sun Viewer 37
A.3.6.1 Assembly Instructions 37
A.3.6.2 Applications 39
A.4 Special Instruments 41
A.4.1 Spectrohelioscope 41
A.4.1.1 Introduction 41
A.4.1.2 Spectroheliograph 41
A.4.1.3 Spectrohelioscope 42
A.4.1.4 Operation of the Veio Spectrohelioscope 42
A.4.1.5 A Scanning Spectrohelioscope by Young 43
A.4.1.6 Spectrohelioscope Resolution 44
A.4.1.7 Variants of the Spectrohelioscope 47
A.4.1.8 Concluding Remarks 48
A.4.2 Prominence Attachment 49
A.4.3 Prominence Eyepiece 53
A.4.4 Birefringent Filters 57
A.4.4.1 Introduction 57
A.4.4.2 Operation 57
A.4.4.3 DayStar Filters 59
A.4.5 Observing the Sun by Radioastronomy 61
A.4.5.1 Introduction 61
A.4.5.2 Telescope Systems 63
A.4.5.3 Designing a Receiver System 64
A.4.5.4 Antenna 64
A.4.5.5 Antenna Transmission Lines 65
A.4.5.6 Receiver 65
A.4.5.7 IF Amplifier 66
A.4.5.8 Integrator 66
A.4.5.9 Amplifier and Offset Compensator 66
A.4.5.10 Monitor Amplifier 68
A.4.5.11 Power Supply 69
A.4.5.12 Assembly, Commissioning 70
A.4.5.13 Observation Possibilities 70
A.5 Photography 73
A.5.1 The Photographic Emulsion and its Theory 73
A.5.1.1 Characteristic curve 74
A.5.1.2 Spectral sensitivity curve 76
A.5.1.3 Gamma-time curves 77
A.5.1.4 Resolving power 77
A.5.1.5 Schwarzschild behavior 78
A.5.1.6 Summary 79
A.5.2 Introduction to White Light Photography 79
A.5.3 Cameras, Adapters, and Accessories 81
A.5.3.1 Cameras 81
A.5.3.2 Adapters 83
A.5.3.3 Accessories 83
A.5.4 Photographic observations of the Chromosphere 83
A.5.4.1 Shooting technique and exposure time 84
A.5.4.2 Choosing a photographic emulsion 85
A.5.5 Solar Photography in Violet Light 87
A.5.6 Dark Room Techniques 88
A.5.6.1 Film Processing 88
A.5.6.2 Paper Printing 90
A.6 Evaluating Photographs 93
A.6.1 Microdensitometry/Microphotometry 93
A.6.2 Principle of the Microdensitometer 93
A.6.3 Working Sequence 94
A.6.4 Data Medium 94
A.6.5 Tips on Preparation and Implementation 95
A.6.6 Microdensitometry Applications 95
A.6.7 Final Observations 97
A.7 Digital Image Processing 99
A.7.1 Introduction 99
A.7.1.1 The Image Generating System 100
A.7.1.2 The Frame Grabber 102
A.7.1.3 The Personal Computer 103
A.7.1.4 Archiving Images 103
A.7.1.5 Image Processing Software 104
A.7.2 Planning an Image Processing System 106
A.7.3 Applications 107
A.8 Recording Solar Structure Movements 113
A.8.1 Introduction 113
A.8.2 Areas of Application 113
A.8.3 8-mm Movie Cameras 114
A.8.4 Film Type Availability 117
A.8.5 35-mm Cine-camera 117
A.8.6 Sequential Photographic Prints 118
A.8.6.1 Peg Bar 119
A.8.6.2 Template 120
A.8.6.3 Sequencing the Photographic Prints 121
A.8.6.4 Shooting the Animation Sequence 121
A.8.6.5 Calculating Time Periods 123
A.8.7 Video 125
Part B Solar Observation 129
B.1 Observation 131
B.1.1 Observation Program and Note-keeping 131
B.1.1.1 Introduction 131
B.1.1.2 Recording Observations 131
B.1.1.3 Observation Programs 132
B.1.2 Seeing 134
B.1.2.1 Introduction 134
B.1.2.2 Appearance 134
B.1.2.3 Defining Turbulence 134
B.1.2.4 The Causes of Seeing 135
B.1.2.5 Daily and Annual Cycles and Other Effects 136
B.1.2.6 Place of Observation 137
B.1.2.7 Concluding Remarks 139
B.2 Sunspots 141
B.2.1 The Structure of Sunspots 141
B.2.1.1 Introduction 141
B.2.1.2 Nomenclature 141
B.2.1.3 Pores 142
B.2.1.4 “Void Areas” 142
B.2.1.5 Umbrae 142
B.2.1.6 Umbral Dots 143
B.2.1.7 Bright Points 143
B.2.1.8 Light Bridges 143
B.2.1.9 Inner Bright Ring 144
B.2.1.10 Outer Bright Ring 144
B.2.1.11 Penumbra 144
B.2.1.12 Other Characteristics 146
B.2.2 The Development of Sunspots and Sunspot Groups 146
B.2.2.1 Typical Development of a Large Area of Activity 146
B.2.2.2 Sunspot Classes and Lifetime 152
B.2.2.3 The Area of a Group 154
B.2.2.4 Number of Individual Sunspots 156
B.2.2.5 Axis Inclination 157
B.2.2.6 Relationship between the Umbra and Penumbra Areas 158
B.2.2.7 Brightness of the Umbra 158
B.2.2.8 Rapid Development of Sunspot Groups 158
B.2.3 Classification of Sunspots and Sunspot Groups 161
B.2.3.1 Waldmeier Classification 161
B.2.3.2 McIntosh Classification 163
B.2.3.3 Kunzel Classification 167
B.2.3.4 Area Classification 167
B.2.3.5 Magnetic (Mt. Wilson) Classification 168
B.2.3.6 Schulze’s Umbra Classification 168
B.2.4 Measurements of Sunspot Activity 170
B.2.4.1 The Sunspot Number 170
B.2.4.2 Group Number g 172
B.2.4.3 The Individual Spot Number f 173
B.2.4.4 Weighting Factor 10 for the Group Number 174
B.2.4.5 Reduction Factor k 175
B.2.4.6 Influences on the k Factor 177
B.2.4.7 Area Number A 182
B.2.4.8 The New Area Number According to Beck 190
B.2.4.9 The Paderborn Sunspot Number 192
B.2.4.10 The Pettis Sunspot Number 193
B.2.4.11 The Activity Area Number 193
B.2.5 Temporal Changes in Sunspot Activity 198
B.2.5.1 Wolf Number Observer Networks 198
B.2.5.2 Averaging of Sunspot Numbers with Time 199
B.2.5.3 The 11 Year Solar Activity Cycle 201
B.2.5.4 The Waldmeier Laws 205
B.2.5.5 The Long Sunspot Cycle 210
B.2.5.6 Long-Term Sunspot Forecasting 213
B.2.6 Naked-Eye Sunspot Observations 215
B.2.6.1 Introduction 215
B.2.6.2 Systematic Observations by Unaided Eye 215
B.2.6.3 The 11-Year Sunspot Cycle Registered by Naked-Eye Observations 216
B.2.6.4 Visibility Limit of the Naked-Eye Sunspots 218
B.3 Position Determination 221
B.3.1 Introduction 221
B.3.2 Observation Methods 222
B.3.2.1 Heliographic Coordinates 222
B.3.2.2 Visual Methods of Determining Positions 225
B.3.2.3 Distortion 232
B.3.2.4 Photographic Observation 235
B.3.2.5 Reducing the Position Coordinates to Heliographic Coordinates 239
B.3.2.6 Applied Position determination, Calculationnewline Example 243
B.3.3 Suggestions for Evaluation 246
B.3.3.1 Mapping the Sun 246
B.3.3.2 Sunspot Distribution 248
B.3.3.3 Extension Measurement of Sunspot Groups 252
B.3.3.4 Axis Inclination of Bipolar Sunspot Groups 256
B.3.3.5 Inherent Motion in Sunspot Groups 257
B.3.3.6 Differential Rotation 259
B.4 Wilson Effect 263
B.4.1 Historical Background 263
B.4.2 Present-day Problems 265
B.4.3 Observation Programs for the Amateur 267
B.4.3.1 Measure of Strength of the Wilson Effect 267
B.4.3.2 Visual Observation of the Wilson Effect 268
B.4.3.3 Photographic Measurement of the Wilson Effect 268
B.4.4 Evaluating Wilson Effect Observations 269
B.4.4.1 Extent of the Umbra and Penumbra 270
B.4.4.2 Evaluating the “Crater Mound” 271
B.4.4.3 Perspective Correction 272
B.4.4.4 Conclusion 273
B.5 Light Bridges 275
B.5.1 Introduction 275
B.5.2 General Features 275
B.5.3 The Development of Light Bridges 277
B.5.4 The Classification of Light Bridges 280
B.5.5 Physical Parameters 282
B.5.6 Suggestions for Research 283
B.5.6.1 Studying Visual Observations 283
B.5.6.2 Distribution Statistics 284
B.5.6.3 Position in the Magnetic Field 285
B.5.6.4 Light Bridge Granulation 285
B.6 Photospheric Faculae 287
B.6.1 Appearance of Faculae 287
B.6.2 Instruments 288
B.6.3 Observation 288
B.6.3.1 Facula Activity 288
B.6.3.2 Types and Classification of Faculae 290
B.6.3.3 Latitudinal Distribution and Position Measurement 292
B.6.3.4 Area 293
B.6.3.5 Brightness 294
B.6.3.6 Lifetime of Dot-Shaped Faculae 295
B.6.3.7 Polar Faculae 295
B.6.3.8 Recording Observations 298
B.7 Granulation 305
B.7.1 Introduction 305
B.7.2 Description 305
B.7.3 Development and Lifespan 307
B.7.4 Some Other Features 308
B.7.5 Short Theory of Granulation 308
B.7.6 Options for the Amateur 308
B.8 Amateur Magnetic Field Observation 309
B.8.1 Introduction 309
B.8.2 Magnetic Field Strength 309
B.8.3 Polarity Distribution 310
B.8.4 Applications 312
B.9 Solar Observation in H alpha Light 313
B.9.1 Introduction 313
B.9.1.1 What is H alpha? 315
B.9.1.2 H Filters 316
B.9.1.3 What does the frequently encountered expression
“full width at half maximum” (FWHM) mean? 317
B.9.2 Choice of Instruments 317
B.9.2.1 Spectrohelioscope 317
B.9.2.2 Prominence Telescope/Attachment 318
B.9.2.3 Lyot Filter 318
B.9.3 Chromosphere 321
B.9.3.1 Historical Background 322
B.9.3.2 Structures of the Quiet Chromosphere 323
B.9.3.3 Structures of the Active Chromosphere 324
B.9.4 Prominences/Filaments 326
B.9.4.1 Observation Records 326
B.9.4.2 Classifications 329
B.9.4.3 Types of Prominences According to Völker 337
B.9.4.4 Observation Programs 338
B.9.4.5 Prominence Statistics 342
B.9.4.6 Filament Statistics 347
B.9.4.7 Determining the Position of Chromospheric Phenomena 348
B.9.4.8 Measuring the Velocities of Prominences 352
B.9.4.9 Measuring the Velocity of Filaments 355
B.9.5 Flares 359
B.9.5.1 History 359
B.9.5.2 The Flare Phenomenon 360
B.9.5.3 Light Curve 361
B.9.5.4 Types of Flares 362
B.9.5.5 Observation Records 363
B.9.5.6 Classification 367
B.9.5.7 Observation Programs 368
B.9.6 Chromospheric Faculae (Plages) 372
B.10 The Aurora 375
B.10.1 Introduction 375
B.10.2 Appearance of the Aurora 375
B.10.3 Source of the Aurora 377
B.10.4 Spectroscopy 380
B.10.5 Photographing the Aurora 381
B.10.6 Stereoscopic photography 382
B.10.7 Visual Observation 383
B.10.8 The Radio Aurora 386
B.10.9 The Magnetic Storm 389
B.10.10 Plotting of Observations 391
B.10.11 Conclusion 393
Part C Solar Eclipses 395
C.1 An Introduction to Solar Eclipses 397
C.1.1 Preparing an Expedition to Observe a Solar Eclipse 397
C.1.1.1 Long-term Preparations 397
C.1.1.2 Medium-term Preparations (about one year before
the eclipse) 397
C.1.2 Visual Observations of Total Solar Eclipses 400
C.1.3 Photographic Observations 402
C.1.3.1 White Light Photographs of the Corona 402
C.1.3.2 Filming the Corona 408
C.1.3.3 Evaluating the Photographs 410
C.1.4 Photocells 411
C.1.4.1 Optoelectronic Recording of the Solar Corona 411
C.1.4.2 Optoelectronic Recording of “Shadow Bands” 412
C.1.5 Meteorological Observations 412
C.1.6 General Photographic Data 413
C.2 Observable Phenomena 415
C.2.1 Flash Spectrum 415
C.2.2 Corona Shapes and Parameters 418
C.2.3 Polarization of the Corona 421
C.2.4 Infrared Corona and Coronal Lines 425
C.2.4.1 569.4 nm 427
C.2.4.2 530.3 nm 427
C.2.4.3 637.4 nm 427
C.2.5 Phenomena in the Solar Corona 428
C.2.6 Movements in the Corona 431
C.2.7 Relationships between the Corona and Prominences 433
C.2.8 Historic Eclipses of the Sun 436
C.2.9 Relativistic Light Bending 438
Part D A Survey of Solar Astronomy Literature 441
D.1 The Survey 443
D.1.1 Books For Amateur Solar Observers 443
D.1.2 Books For the Layman Published Before 1950 444
D.1.3 Books For the Layman Published After 1950 445
D.1.4 Monographs for professional astronomers 447
D.1.5 Journals About the Sun 454
Bibliography 457
Appendix A Supplier Sources 503
A.1 Sources 503
A.2 NASA Solar Eclipse Bulletins 506
A.3 Daily Coronal Images 506
A.4 National and International Associations of Amateur Solar Observers 507
Index 511