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Edited by Albert Ingalls

Volume 1,
Subjects covered: Newtonian Telescope Mirror Making; Optical Testing; Workshop Wisdom; and Observatory Buildings. 6.00" by 9.00", 590 pages, hardbound,
$29.95

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Volume 2,
Subjects covered: Refractor Telescopes; Telescope Mechanics; Telescope Adjustments; Binoculars; Schmidt Cameras; and Optical Flats. 6.00" by 9.00", 590 pages,
hardbound,
$29.95

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Volume 3, Subjects covered: Optical Production Methods and Machinery; Eyepieces and Small Lenses; Optical Coatings and Coating Equipment; The Eye and Atmosphere; Other Optical Instruments; and Instrumentation for Solar Observations. 6.00" by 9.00", 630 pages, hardbound, 2Lbs. ship wt. $29.95

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About these books:

First, some history about how the Amateur Telescope Making books came to be. In the early 1920s a naturally curious fellow, Albert Ingalls, happened to read an article in an obscure magazine by an even more curious fellow, Russell Porter. The article was about the "Poor Man's" telescope and told the story of how a group of Vermont villagers built their own reflecting telescopes. It was to be a fateful event because Albert Ingalls was an editor of Scientific American magazine and telescope making was about to gain a much larger audience through America's preeminent science magazine. Ingalls and Porter would, during the next 30 years, create and inspire from others a body of literature that would eventually span a three-volume set of books.

Many people are surprised when they find out that the optics for a 6 or 8 inch Newtonian reflecting telescope can be made by hand using the simplest of tools and materials. Since the invention of the telescope about 400 years ago, telescope making has always had an amateur component. Some amateur telescope makers were fascinated by the process itself, while others (like the great observer of the night sky, William Herschel) became amateur telescope makers as a means to their ultimate objective of exploration.

Inevitably some of the more accomplished amateurs became professionals and made instruments for others, but these instruments were never cheap. Until the discovery of methods to coat glass with silver in the mid-1800s the telescope of choice was the refractor—in spite of its price. By the time aluminum replaced silver in the late 1930s, reflectors had almost completely replaced refractors in popularity. This series of books is one of the reasons why.

The ATM books were originally published at a time when it was costly to rearrange the contents once it was set in type, so with each edition and printing new material tended to be added at the back. Over the years they grew larger and less well organized. Yet, because they contained so much valuable information, telescope makers, even today, considered them to be the bible of telescope making.

These books are a rearrangement of the original three-volume work. Insofar as possible similar items are now grouped together; each as a Chapter within a descriptive Part. Chapters are usually divided into sections, subsections, etc. While the Table of Contents for a typical "ATM" of old was 2 pages it is now 3 to 5 times larger. The Index has similarly been expanded. The objective was not to rewrite but to logically rearrange the text into a more user-accessible format. Spelling, hyphenation and usage have been standardized, and errors-in-fact corrected, but almost all the original text remains fundamentally unchanged (pendulum clocks and vacuum tube photoelectric photometry articles were cut) and now makes up nearly 1,800 pages of text and illustrations devoted to practical telescope making.

Tables of Content

Amateur Telecope Making Book 1
A Newtonian Telescope Mirror Making 1
   A.1 Mirror Making for Reflecting Telescopes 3
      A.1.1 Introduction to the Reflecting Telescope 3
      A.1.2 Grinding the Mirror 5
      A.1.3 Making the Pitch Lap 6
      A.1.4 Polishing the Mirror 7
      A.1.5 Testing the Mirror 8
      A.1.6 Figuring the Mirror 11
      A.1.7 Silvering the Mirror 17
      A.1.8 Biographical Note by the Editor 21
      A.1.9 Note Added in 1996 21
   A.2 The Beginner's First Telescope 25
      A.2.1 Editor's Note 25
      A.2.2 Introduction 26
      A.2.3 The Poor Man's Telescope 28
      A.2.4 The Main Thing is the Mirror 30
      A.2.5 And So— 33
      A.2.6 Now We Start 35
      A.2.7 Keep Hogging 36
      A.2.8 Checking Progress 38
      A.2.9 No More Long Strokes 40
      A.2.10 Scratches 42
      A.2.11 Polishing 43
      A.2.12 All Set to Begin Polishing 44
      A.2.13 Mounting the Poor Man's Telescope 48
      A.2.14 Collimation 53
      A.2.15 Albert G. Ingalls Editor's Note 56
      A.2.16 Notes Added in 1996 62
  A.3 The HCF Lap 63
      A.3.1 Advantages of HCF 63
      A.3.2 Making and Using an HCF Lap 64
      A.3.3 Using HCF for Zonal Correction 66
   A.4 The Amateur's Telescope 69
      A.4.1 Introductory 69
      A.4.2 Literature 71
      A.4.3 Tools and Materials 72
      A.4.4 Rough Grinding 74
     A.4.5 Testing; Foucault's Shadow Test 79
      A.4.6 Polishing 83
      A.4.7 Figuring 87
         A.4.7.1 Parabolizing by Long Stroke 88
         A.4.7.2 Parabolizing by Graduating Facets 89
         A.4.7.3 Parabolizing by the Small Polisher System 90
         A.4.7.4 Parabolizing by Overhang 90
         A.4.7.5 Working Uphill 91
      A.4.8 Editor's Note 94
      A.4.9 How to Recognize the Paraboloid, Zonal Testing 95
       A.4.10 Silvering 101
         A.4.10.1 To Polish the Film 101
         A.4.10.2 A Few Hints on Silvering 102
         A.4.10.3 Care of the Film 103
         A.4.11 Mounting the Mirror 104
         A.4.12 A Last Word to Beginners on Insufficient Grinding 107
    A.5 An Amateur's View of Mirror Making 111
      A.5.1 From One TN to Another 111
            A.5.1.1 Pitch 111
            A.5.1.2 Abrasive Action, Rolling and Stationary 111
            A.5.1.3 The Spit Test for Radius of Curvature 112
            A.5.1.4 Tool Effect 113
            A.5.1.5 Thermal Effect 113
            A.5.1.6 Evaporation Effect 114
            A.5.1.7 Friction Effect 116
            A.5.1.8 Tool Deformation 117
            A.5.1.9 Tool Plowing 118
            A.5.1.10 The Clock Stroke 118
            A.5.1.11 The Blending Overhand Stroke 119
            A.5.1.12 The Semistroke 120
                 A.5.2 Backwoods Technique 120
            A.5.2.1 The Handle 120
            A.5.2.2 The Grip 120
            A.5.2.3 Rough Grinding 121
            A.5.2.4 Fine Grinding 123
            A.5.2.5 The Lap 124
            A.5.2.6 Polishing 127
            A.5.2.7 Correcting 128
            A.5.2.8 Figuring 134
      A.5.3 The Second Mirror 135
      A.5.4 In Retrospect 136
   A.6 Subdiameter Tools 139
      A.6.1 Large Mirrors and Subdiameter Tools 139
      A.6.2 Use of Subdiameter Tools on a 12-inch Mirror 140
      A.6.3 Use of Subdiameter Tools on a 10-inch Mirror 141
      A.6.4 Construction of Subdiameter Tools 144
  A.7 The Prism or Diagonal 147
      A.7.1 Editor's Notes 151
      A.7.2 Sizing a Newtonian Diagonal 151
         A.7.2.1 Addendum, 1948 154
   A.8 Prism Diagonals-Axial Aberration Effects 157
      A.8.1 Axial Spherical Aberration 158
      A.8.2 Axial Chromatic Aberration 159
      A.8.3 Effect on Definition 160
      A.8.4 Extra-Axial Aberrations 161
      A.8.5 Prism Glasses 162
   A.9 How to Make a Diagonal for a Newtonian 163
      A.9.1 Making the Blank 163
      A.9.2 Making a ``Surround'' 164
      A.9.3 Grinding 165
      A.9.4 Polishing 166
      A.9.5 Testing for Flatness 166
      A.9.6 Mounting the Diagonal 167
   A.10 The Building of a 19-Inch Reflecting Telescope 169
      A.10.1 The Mirror 170
            A.10.2 Mounting 178
      A.10.3 The Clock 184
         A.10.4 Note Added in 1996 186
B Optical Testing 187
   B.1 Curves Found During Figuring 189
  B.2 Where Is The Crest Of The Doughnut? 197
      B.2.1 A Study in Shadows 197
   B.3 Accuracy in Parabolizing a Mirror 201
      B.3.1 Editor's Note 206
      B.3.2 Note Added in 1996 207
   B.4 The Ronchi Test for Mirrors 209
      B.4.1 Note Added in 1996 214
   B.5 Hindle's Method in the Knife-edge Test 215
   B.6 The Slit Test 219
   B.7 Shadow Appearance 223
      B.7.1 Doughnut Mathematics 225
      B.7.2 Shadow Behavior 231
      B.7.3 The Error of Observation 235
      B.7.4 Accuracy of the Knife-edge Test 238
      B.7.5 Testing Equipment 240
      B.7.6 Testing Routine 243
      B.7.7 Note Added in 1996 248
  B.8 The Caustic Test 251
      B.8.1 Caustic Testing Procedure 262
      B.8.2 Interpretation 265
      B.8.3 Sample Calculations 266
      B.8.4 Test Rigs 268
         B.8.4.1 Test Rig for Second Method 269
         B.8.4.2 Test Rig for Third Method 269
      B.8.5 Accuracy 276
      B.8.6 Nonparaboloidal Surfaces 280
      B.8.7 Editor's Note 281
      B.8.8 Note Added in 1996 283
   B.9 Quantitative Optical Test for Telescope Mirrors 285
      B.9.1 Quantitative Failure of Test 285
      B.9.2 Apparatus and Procedure 286
      B.9.3 Geometry of Test 288
      B.9.4 Appearances of Common Forms of Aberration 289
      B.9.5 Editor's Note 289
      B.9.6 Notes on the Ronchi Band Patterns 290
      B.9.7 Note Added in 1996 292
   B.10 Gregorian Secondary Test 293
      B.10.1 Editor's Note, 1948 297
  B.11 The Hartmann Test 299
   B.12 Notes on the Optical Testing of Aspheric Surfaces 305
      B.12.1 The Ellipsoid 305
      B.12.2 Testing The Paraboloid On Near Objects 308
      B.12.3 Quantitative Test of Hyperboloidal Mirrors 310
      B.12.4 Note Added in 1996 314
   B.13 Null Test for Paraboloids 315
      B.13.1 Editor's Note 319
  B.14 Testing Convex Spherical Surfaces 321
   B.15 A Bilateral Slit Mechanism 325
   B.16 Small Pinholes 329
      B.16.1 Determining the Optimum Size 329
      B.16.2 Illuminating the Pinhole 331
      B.16.3 Making the Pinhole 332
      B.16.4 Differences in Usage Between Small and Large Pinholes 332
      B.16.5 Note Added in 1996 334
   B.17 Astigmatism 335
   B.18 Optical Bench Testing 34
1
      B.18.1 Introduction 341
      B.18.2 Lens Characteristics 341
      B.18.3 A Nodal Slide Optical Bench 343
         B.18.3.1 Illuminator 344
         B.18.3.2 Telescope-microscope 345
         B.18.3.3 The Optical Bench Proper 347
         B.18.3.4 The Slides X and S 347
      B.18.4 Alignment 347
      B.18.5 Testing Methods 349
         B.18.5.1 Tests on the Axial Image 350
            B.18.5.1.1 Equivalent Focal Length 350
            B.18.5.1.2 Back Focal Length 351
            B.18.5.1.3 Working Distance 351
            B.18.5.1.4 Flange Focal Length 352
            B.18.5.1.5 Axial Critical Aperture Ratio or Aperture Tolerance 352
            B.18.5.1.6 Axial Chromatic Aberrations 353
         B.18.5.2 Axial Spherical and Zonal Aberrations 353
         B.18.5.3 Tests Using Extra-Axial Images 354
            B.18.5.3.1 Curvature of Image Field 354
            B.18.5.3.2 Lateral Chromatic Aberration 357
            B.18.5.3.3 Distortion 357
         B.18.5.4 Comatic, Lateral Spherical or Sinical Aberration 358
         B.18.5.5 Astigmatism 358
         B.18.5.6 Testing Complete Telescopes 359
            B.18.5.6.1 Convergent Tubes 362
            B.18.5.6.2 General Caution 363
      B.18.5.7 Approximate Refractometry 363
         B.18.5.7.1 Radius Measurement in General 365
      B.18.6 Summary 366
      B.18.7 References 367
   B.19 Interference of Light 369
      B.19.1 Newton's Fringes 374
      B.19.2 Haidinger's Fringes 378
      B.19.3 Low-reflection Coatings 380
      B.19.4 Diffraction 383
      B.19.5 Image Spikes 383
      B.19.6 Focal Diffraction 387
         B.19.6.1 Edge Diffraction 387
      B.19.7 Refractor vs. Reflector 392
   B.19.8 References 392
   B.19.9 Notes Added in 1996 393
C Workshop Wisdom 395
   C.1 Advice From TN's 397
      C.1.1 General 397
         C.1.1.1 Choosing a Mirror Size 397
         C.1.1.2 Walking Around the Barrel 397
         C.1.1.3 The Correct Level for Grinding and Polishing 398
         C.1.1.4 Flexure 398
         C.1.1.5 Warping of Wood on which Tool is Mounted 398
         C.1.1.6 Uniform Working Temperature 399
         C.1.1.7 Keep a Log Book 399
         C.1.1.8 Sagitta equals r2/2R 400
         C.1.1.9 When r2/2R is not exact enough 400
         C.1.1.10 Scratches 402
         C.1.1.11 Mirror Breakage 403
         C.1.1.12 Workplace Cleanliness 403
         C.1.1.13 Shipping a Mirror 404
         C.1.1.14 Take Courage 404
         C.1.1.15 Three in One 405
      C.1.2 Mirror Substrates 405
         C.1.2.1 Fused Quartz 405
         C.1.2.2 Pyrex 406
         C.1.2.3 How Plate Glass is Made 407
         C.1.2.4 Optical Glass 407
         C.1.2.5 Glass Mirror Substitutes 408
         C.1.2.6 Rotating Mercury Mirror 412
         C.1.2.7 Cellular Mirror 413
         C.1.2.8 Cemented, Built-Up Disks 415
         C.1.2.9 Suction Mirror 416
         C.1.2.10 Magnesium Oxychloride Mirror 416
      C.1.3 Cutting Circular Disks and Holes 417
      C.1.4 Tools and Fixtures 418
         C.1.4.1 Inverting Tool and Mirror 418
         C.1.4.2 Inverting Device 419
         C.1.4.3 Limiting Devices 419
         C.1.4.4 Making Templates 420
         C.1.4.5 Metal Template 420
         C.1.4.6 Removable Handle for Mirror Disks 421
         C.1.4.7 Grinding Stands 421
      C.1.5 Grinding Abrasives 421
         C.1.5.1 Designations for Carbo Grain Sizes 421
         C.1.5.2 Crushed Steel and Pyrex 422
      C.1.6 Grinding 422
         C.1.6.1 Who Discovered the Method of Concaving a Glass Disk? 423
         C.1.6.2 Nature of Grinding 424
         C.1.6.3 Wets 424
         C.1.6.4 One-third Strokes 424
         C.1.6.5 Strokes in Grinding 425
         C.1.6.6 Why Disks Grind Concave 426
         C.1.6.7 Refusal of the Mirror to Become Concave 426
         C.1.6.8 Amount of Glass Removed for Each Stage 427
         C.1.6.9 Chamfering Disks 428
         C.1.6.10 Getting Overall Contact while Grinding 428
         C.1.6.11 Bad Central Contact in Final Grinding 429
         C.1.6.12 Estimating Fineness of Grinding 430
         C.1.6.13 Streak of Rouge Test for Contact in Fine Grinding 431
         C.1.6.14 Water Drop Test for Contact in Fine Grinding 431
         C.1.6.15 Sticking Mirror 431
         C.1.6.16 Mirror Sticks to Tool 432
         C.1.6.17 Get a Sphere before Beginning to Polish 433
         C.1.6.18 When is Fine Grinding Finished? 434
         C.1.6.19 Finishing With Emery 434
         C.1.6.20 Searching for Tiniest Pits 435
         C.1.6.21 Futility of Attacking Big Pits with Rouge 435
         C.1.6.22 Test for Center of Curvature During Grinding 437
         C.1.6.23 Keeping Track of the Radius of Curvature While Grinding 437
         C.1.6.24 Very Exactly Finding the Radius of Curvature 438
         C.1.6.25 Bubbles Between Mirror and Tool 438
      C.1.7 Pitch Laps 438
         C.1.7.1 Pitch 438
         C.1.7.2 Making the Pitch Lap 439
         C.1.7.3 Modifications of the Plain Pitch Lap. 444
         C.1.7.4 Straining Pitch 445
         C.1.7.5 Speckling of lap 445
         C.1.7.6 Pitch Flammability 446
         C.1.7.7 Channels in Laps 446
      C.1.8 Nonpitch Laps 446
         C.1.8.1 The HCF Lap 446
         C.1.8.2 The Paper Polishing Lap 449
         C.1.8.3 Laps in Hot Places 450
         C.1.8.4 Substitutes for Pitch 450
      C.1.9 Polishing Agents 450
         C.1.9.1 Rouge Size 450
         C.1.9.2 How to Make Rouge 450
            C.1.9.2.1 Editor's Note 452
      C.1.10 Another Method for Making Rouge 453
      C.1.11 Breaking-up Rouge 453
      C.1.12 Polishing 453
         C.1.12.1 Polishing, Theory 453
         C.1.12.2 Grabbing 459
         C.1.12.3 Sleeks 460
         C.1.12.4 Scratches From Rouge 460
         C.1.12.5 Stuck Disks 460
         C.1.12.6 Test for Complete Polish 461
         C.1.12.7 Detecting the Most Minute Pits and Scratches 461
         C.1.12.8 Cold Pressing 461
         C.1.12.9 Prolonged Cold Pressing 461
      C.1.13 Figuring 462
         C.1.13.1 Correcting Turned-up Edge 462
         C.1.13.2 Correcting a Hole 462
         C.1.13.3 Correcting a Hyperbola 463
         C.1.13.4 Forestalling Turned-down Edge 463
         C.1.13.5 Turned-down Edge 463
         C.1.13.6 Turned Edge 463
         C.1.13.7 Test for Slight Turned Edge 464
         C.1.13.8 Diffraction Effects 465
      C.1.14 Testers 465
         C.1.14.1 A Cool Pinhole 465
         C.1.14.2 Permissible Distance Differential of Pinhole
                         and Knife-edge along the Axis 466
         C.1.14.3 Electric Lamp for Knife-edge Test 466
         C.1.14.4 Tiny Pinhole for Advanced Workers 467
         C.1.14.5 Slow Motion Devices for Testing 467
         C.1.14.6 Reversing Knife-edge 467
         C.1.14.7 Testing Tunnel 468
      C.1.15 Testing 468
         C.1.15.1 First Announcement of Foucault Test 469
      C.1.16 Conic Sections 471
      C.1.17 Record Keeping 473
      C.1.18 Correct Paraboloidal Shadow 475
         C.1.18.1 Measuring Zones 476
         C.1.18.2 Testing without Masks 477
         C.1.18.3 Interpreting Shadows 478
         C.1.18.4 Precision in Reading Knife-edge Shadows 479
         C.1.18.5 The Inside-and-outside Test 480
            C.1.18.5.1 Editor's Note 481
            C.1.18.6 Learning to Understand the Knife-Edge Test 482
            C.1.18.7 Avoiding Fatigue in the Knife-edge Test 483
            C.1.18.8 Making Focograms 484
            C.1.18.9 Diffraction Ring (Star) Test 486
      C.1.19 Abnormalities 493
         C.1.19.1 Warped Mirror 493
         C.1.19.2 Astigmatized Mirror 494
         C.1.19.3 Striae 494
         C.1.19.4 Strains in Glass and Their Detection 494
         C.1.19.5 Editor's Note 497
      C.1.20 Notes on the Eyepiece 498
      C.1.21 Telescope Mechanics 502
         C.1.21.1 Tubeless Telescope 502
         C.1.21.2 Hardening Brass 502
         C.1.21.3 Blackening Brass 502
         C.1.21.4 Paint for Inside of Tube 502
          C.1.21.5 An Adapter Tube 502
         C.1.21.6 Finders 503
         C.1.21.7 More about Finders 504
   C.1.22 Telescope Designs 505
      C.1.22.1 Ritchey-Chrétien 505
      C.1.22.2 Cassegrainian Notes 507
      C.1.22.3 The Herschelian Telescope 514
   C.1.23 Literature of Interest to the TN 515
      C.1.23.1 Observatories 515
      C.1.23.2 Herschel's Mirrors 516
      C.1.23.3 Properties of Pitch 517
      C.1.23.4 Wassell and Blacklock Letters 517
   C.1.24 Graduating Setting Circles 517
D Observatory Buildings 5199
   D.1 Telescope Housings 521
      D.1.1 The Warmed Observing Room 521
      D.1.2 Turret Telescopes 523
   D.2 The Amateur's Observatory 527
      D.2.1 Observatory Size 530
      D.2.2 Weatherproofing 531
      D.2.3 Rollers 531
      D.2.4 The Sliding Roof Observatory 532
      D.2.5 Domes 534
         D.2.5.1 Shutters 543
         D.2.5.2 Revolving the Dome 544
   D.3 Thermal Effects of Observatory Paints 549
      D.3.1 Introduction 549
      D.3.2 Test Procedures 549
      D.3.3 Interior painting 552

Amateur Telecope Making Book 2
A Refractor Telescopes 1
   A.1 Reflectors versus Refractors 3
      A.1.1 Introduction 3
      A.1.2 An Inexpensive Mounting and Shelter 4
         A.1.2.1 The Question of Air Currents in the Tube 7
         A.1.2.2 The Diffraction Rings 11
   A.2 The Achromatic Object Glass 15
      A.2.1 Calculating Curves. First step 16
      A.2.2 Practical---Shaping and Grinding 25
      A.2.3 Polishing 29
      A.2.4 Testing and Figuring 30
      A.2.5 Mounting the Lens 36
      A.2.6 Editor's Notes 40
         A.2.6.1 Measuring Edge Thickness 40
         A.2.6.2 Conventions Used in Designing Objective Lenses 40
      A.2.7 Biographical Note 41
   A.3 The Refractor—Design and Construction 43
      A.3.1 Editor's Note 43
      A.3.2 Introduction and Theoretical Considerations 44
      A.3.3 Making an Achromatic Object Glass 74
         A.3.3.1 Making a Flat for Testing 74
         A.3.3.2 Spherometers 77
         A.3.3.3 And So To Work 79
         A.3.3.4 Metal Laps 80
         A.3.3.5 Grinding the Curves 85
         A.3.3.6 Edge Thickness 87
         A.3.3.7 Ronchi-Testing the Lens 88
         A.3.3.8 Centering 90
         A.3.3.9 The Cell 92
         A.3.3.10 Cementing 93
         A.3.4 Note Added in 1996 98
   A.4 The Refractor—Metal Parts and Mounting 101
      A.4.1 Size 102
      A.4.2 Material 103
      A.4.3 Costs 105
      A.4.4 Practical 105
      A.4.5 Machining the Main Tube 106
      A.4.6 The Cell 108
         A.4.6.1 The Outer Cell 110
      A.4.7 Cell Assembly Made from Heavy-wall Tubing 112
      A.4.8 The Control End 114
      A.4.9 The Focus Control 114
      A.4.10 Finish 118
      A.4.11 Assembling the Parts 118
      A.4.12 Diaphragms 119
      A.4.13 The Mounting 120
   A.4.14 The Tripod 121
   A.5 Design of Refractors by the G-sum Method 125
      A.5.1 Introduction 125
      A.5.2 Sign Convention 126
      A.5.3 Design of a Cemented Doublet 127
      A.5.4 Design of a Fraunhofer Type Objective 130
         A.5.4.1 Airspacing 132
      A.5.5 Barlow Lens 134
      A.5.6 Thickness 134
      A.5.7 Conclusions 135
      A.5.8 Note Added in 1996 138
   A.6 Design of Refractors by Ray Tracing 139
      A.6.1 The Ray Trace Method 139
      A.6.2 The Equations of Ray Tracing 141
         A.6.2.1 Lens Aberrations 145
         A.6.2.2 Spherical Aberration 146
         A.6.2.3 Coma and OSC 146
         A.6.2.4 Chromatic Aberration 148
         A.6.2.5 The Path-Difference Method 151
      A.6.3 Ray Trace Design Procedure 155
      A.6.4 In Conclusion 172
   A.7 Computing the Radii of an Achromatic Objective 177
      A.7.1 Editor's Note 177
      A.7.2 Introduction 177
   A.8 Optical Glass Procurement 189
B Telescope Mechanics 197
   B.1 Telescope Mounts 199
      B.1.1 Making the Mounting 199
   B.2 Telescope Mounting Design Fundamentals; Rigidity 215
      B.2.1 The Tube 225
      B.2.2 The Mirror Cell 226
      B.2.3 Machining 230
      B.2.4 Résumé 232
      B.2.5 Note Added in 1996 232
   B.3 A Motor Drive for the Telescope 233
   B.4 Telescope Drives 237
      B.4.1 Drives for Larger Telescopes 254
      B.4.2 Drive for a 12.5" Fork Type Reflector 255
      B.4.3 Drive for a 14 reflector 257
      B.4.4 Note Added in 1996 261
   B.5 Hand-wound Spring Drives for Telescopes 263
      B.5.1 Ordinary Clockwork Gramophone Motor 263
      B.5.2 Combination Spring Motor and Weight-driven Assemby 265
      B.5.3 Spring-driven Phonograph Motor Drive 266
      B.5.4 "Hempstead Hydrant'' Mount 268
   B.6 The Springfield Mounting 271
      B.6.1 General Description 272
      B.6.2 Pattern Making for the Springfield Mounting 277
         B.6.2.1 Making the Actual Pattern 285
      B.6.3 Casting 286
      B.6.4 Molding and Casting Springfield Mounting Parts 287
         B.6.4.1 Editor's Note 287
         B.6.4.2 Introduction 287
         B.6.4.3 The Furnace 288
         B.6.4.4 The Crucible, and Tools to Handle it 289
         B.6.4.5 Cope and Drag 290
         B.6.4.6 Other Equipment 291
         B.6.4.7 Molding Sand 292
         B.6.4.8 Molding 293
         B.6.4.9 Pouring the Metal 297
         B.6.4.10 Brasses, Bronzes and Miscellaneous 298
      B.6.5 Machining the Springfield Mounting 300
         B.6.5.1 Miscellaneous 303
      B.6.6 Motor Drives, Counterweighting, Pier 306
         B.6.6.1 Counterweighting 309
         B.6.6.2 The Pier 309
   B.7 Molding and Casting a Fork 313
      B.7.1 Editor's Note 313
      B.7.2 The Mold 313
      B.7.3 Casting 316
   B.8 Mechanical Flotation of Mirrors 319
      B.8.1 3-point Support 321
      B.8.2 18-point Support 322
      B.8.3 9-point Support 324
      B.8.4 Note Added in 1996 326
   B.9 Cork Insulation for Reflecting Telescopes 329
   B.10 Making Setting Circles—a Composite Chapter 333
      B.10.1 Editor's Note 333
      B.10.2 Editor's Note on Dividing Heads 341
      B.10.3 Correction of Periodic Inequalities 346
      B.10.4 Editor's Note 349
   B.11 Wooden Tubes for Reflectors—a Composite Chapter 351
  B. 12 Dealing with Spider Diffraction 357
      B.12.1 Note Added in 1996 360
C Telescope Adjustments 361
   C.1 Collimation and Adjustment 363
      C.1.1 Collimation 363
      C.1.2 Adjusting the Polar Axis 366
      C.1.3 Indoor Adjustment of an Equatorial 367
         C.1.3.1 Theory 370
      C.1.4 Adjusting Telescope by Equatorial Star 375
D Binoculars 377
   D.1 The Overhaul and Adjustment of Binoculars 379
      D.1.1 Types of Binoculars 380
      D.1.2 Modern Binoculars 383
         D.1.2.1 Body 383
         D.1.2.2 Hinge 384
         D.1.2.3 Objective Assembly 385
         D.1.2.4 Lubricants 386
         D.1.2.5 Waxes 387
         D.1.2.6 Ocular Assembly 388
         D.1.2.7 Prism Assembly 389
         D.1.2.8 Covering and Finishes 392
         D.1.2.9 Tolerances 393
            D.1.2.9.1 Body Castings and Hinges 393
            D.1.2.9.2 Objective Fittings 394
            D.1.2.9.3 Ocular Parts 394
            D.1.2.9.4 Prism Plates 394
         D.1.2.10 Optical System 394
            D.1.2.10.1 Objective, Crown Lens 395
            D.1.2.10.2 Objective, Flint Lens 397
            D.1.2.10.3 Prisms 397
            D.1.2.10.4 Ocular Field Lens 397
            D.1.2.10.5 Crown Eyelens 397
            D.1.2.10.6 Flint Eyelens 397
         D.1.2.11 Checking and Matching Prisms 399
         D.1.2.12 Centering and Cementing Lenses 403
         D.1.2.13 Collimation 406
      D.1.3 Semimodern Binoculars 412
      D.1.4 Binoculars with Central Focusing Devices 414
      D.1.5 Galilean Type Binoculars (Field Glasses) 416
      D.1.6 Evaluating a Binocular 417
E Schmidt Cameras 421
   E.1 The Schmidt Camera---Introductory 423
      E.1.1 Editor's Note 429
   E.2 Theory and Design of Aplanatic Reflectors 433
   E.3 Notes on the Construction of an F/1 Schmidt Camera 443
   E.4 Schmidt Camera Notes 451
      E.4.1 Focal Length 451
      E.4.2 The f-Number, or Speed 452
      E.4.3 Vignetting 453
      E.4.4 Construction 455
         E.4.4.1 Mirror 455
         E.4.4.2 Correcting Plate 457
      E.4.5 Testing 459
      E.4.6 The Mounting 462
      E.4.7 Portability 465
      E.4.8 Editor's Note 470
   E.5 Note on Figuring Schmidt Correcting Plates 473
      E.5.1 Autocollimation Test for Schmidt Cameras 475
   E.6 The Construction of a Schmidt Camera 479
      E.6.1 Note Added in 1996 483
   E.7 Further Notes on Schmidt Cameras 485
      E.7.1 References 491
      E.7.2 Bibliography 491
   E.8 Applications of the Schmidt Principle in Optical Design 493
      E.8.1 Applications of the Schmidt Principle 496
      E.8.2 The Design and Construction of Correcting Plates 499
      E.8.3 Editor's Note 504
   E.9 Bernhard Schmidt and His Reflector Camera 507
      E.9.1 Editor's Note 512
   E.10 A Rapid Coma-Free Mirror System 517
F Optical Flats 521

     F.1 Optical Flats 523
         F.1.1 Editor's Note 528
   F.2 Making Astronomical Flats 529
   F.3 Flats 535
      F.3.1 Raw Materials 535
      F.3.2 Preliminary Work 537
      F.3.3 Grinding 539
      F.3.4 Polishing 540
      F.3.5 Figuring 540
      F.3.6 Testing 544
      F.3.7 Special Applications 549
         F.3.7.1 Diagonals 549
      F.3.8 Plane-parallels 549
      F.3.9 Accuracy 553
      F.3.10 Note Added in 1996 554
   F.4 Optical Flats 557
         F.4.1 Materials Suitable for Flats 557
         F.4.2 Making a True Surface 558
         F.4.3 Polishing and Correcting 559
         F.4.4 Testing 560

Amateur Telescope Making Book 3
A Optical Production Methods and Machinery 1
   A.1 Grinding and Polishing Machines 3
      A.1.1 Ritchey's Description of His Machines 8
   A.2 Machine Polishing Mirrors 17
      A.2.1 Types of Machines 18
      A.2.2 Continuous Polishing 20
      A.2.3 Figure Obtained by Machine Polishing 20
      A.2.4 Polishing Face-up 22
      A.2.5 Hypocycloidal Polishing 23
         A.2.6 Editor's Note 25
   A.3 Making and Using Metal Laps 27
      A.3.1 Concave Tools 27
      A.3.2 Convex Tools 28
      A.3.3 On Using Metal Tools 30
      A.3.4 Polishing 32
      A.3.5 Editor's Note 33
   A.4 Lens Production 35
      A.4.1 Lens Generating 35
      A.4.2 Rough Grinding After Milling 40
      A.4.3 Templates 42
      A.4.4 Making and Use of Proof Plates 45
       A.4.5 Metal Tools 49
      A.4.6 Blocking Lenses in Multiple and Single Units 52
      A.4.7 The Strokes of Grinding and Polishing 57
      A.4.8 Forming the Lap 61
      A.4.9 Abrasives: Garnet Fines, Barnesite, Cerium Oxide, Rouge 62
         A.4.9.1 Silicon Carbide 65
         A.4.9.2 Aluminum Oxide (synthetic corundum)65
         A.4.9.3 Natural Corundum 65
         A.4.9.4 Natural Garnet 65
      A.4.10 Surface Inspection During Polishing and Afterward 66
      A.4.11 Centering and Edging 67
      A.4.12 Cementing of Lenses 69
      A.4.13 Degreasers: Cleaning 73
   A.5 Prisms, Flats, Mirrors 77
      A.5.1 Editor's Introduction 77
      A.5.2 Prisms 78
         A.5.2.1 Errors and Tolerances78
         A.5.2.2 Glass 79
         A.5.2.3 Commercial Production Procedure 80
         A.5.2.4 Requisites for Small-scale Production 82
         A.5.2.5 Procedure for Small-scale Production 85
         A.5.2.6 The Ring Method for Single Units 86
         A.5.2.7 Polishing 87
         A.5.2.8 Testing 90
         A.5.2.9 Hand Correcting 95
      A.5.3 Flats 98
         A.5.3.1 Accent on Grinding 98
         A.5.3.2 Polishing 105
      A.5.4 Mirrors 108
   A.6 A Reflecting Autocollimator 111
   A.7 Making Rhomboid Prisms 125
      A.7.1 Editor's Note 129
B Eyepieces and Small Lenses 131
   B.1 Telescope Oculars 133
         B.1.1 High-power Oculars 136
         B.1.2 Note Added in 1996 137
   B.2 Astronomical Oculars 139
      B.2.1 Huygenian Ocular 140
      B.2.2 Ramsden Ocular 140
     B.2.3 Solid Ocular 141
     B.2.4 A New Solid Ocular 142
  B.3 Telescope Eyepieces 145
      B.3.1 Eyepiece Terminology 155
      B.3.2 Eyepiece Design 159
      B.3.3 Microscope Oculars 162
      B.3.4 Custom-built Eyepieces 163
      B.3.5 War Surplus Eyepieces 163
      B.3.6 Synthesis of Eyepieces 164
      B.3.7 Eyepiece Constructions 164
      B.3.8 Eyepiece Prescriptions 169
      B.3.9 Testing 169
      B.3.10 Series of Eyepieces 171
      B.3.11 References 172
      B.3.12 Note Added in 1996 175
   B.4 The Barlow Lens 177
   B.5 Making Eyepieces 189
   B.6 Small Lens Wrinkles 197
   B.7 An Introduction to Small Lenses 205
      B.7.1 Tools and Curves 206
     B.7.2 The Relationship Between the Focus and Curve 212
      B.7.3 Focus 212
      B.7.4 Making a Lens, Blanks and Roughing 215
      B.7.5 Gauges and Laps 217
         B.7.5.1 Convex (Male) Gauges 217
         B.7.5.2 Concave (Female) Gauges 217
         B.7.5.3 Lap Mandrel 219
         B.7.5.4 Laps 219
         B.7.5.5 Convex Lap 220
         B.7.5.6 Roughing Out 222
         B.7.5.7 Polishing 224
         B.7.5.8 Flat Surfaces 226
         B.7.5.9 Flat Laps 226
         B.7.5.10 Making the Flat Pitch Lap 230
         B.7.5.11 Centering 232
         B.7.5.12 Spinning 234
      B.7.6 Mountings, Fixtures and Jigs 235
         B.7.6.1 Eyelens Caps 237
         B.7.6.2 Finishing and Fitting a Lens Ring to a Lens 237
         B.7.6.3 Fastening the Lens in Its Ring 238
        B.7.6.4 Finishing the Tube 239
         B.7.6.5 Finishing the Eyepiece Cap 239
         B.7.6.6 Applying Black Oxide Finish 240
         B.7.6.7 Glass 240
         B.7.6.8 Eyepiece Specifications 240
   B.8 Measuring Radii of Strongly Curved Surfaces 247
C Optical Coatings and Coating Equipment 259
C.1 Reflective Mirror Coatings 261
C.1.1 Methods of Silvering Glass 261
C.1.1.1 Cleaning the Surface to be Silvered 261
C.1.2 Purity of Chemicals Used 262
C.1.3 Brashear's Process 262
C.1.3.1 Drying, Burnishing, Etc. 264
C.1.3.2 Editor's Note 264
C.1.4 Instructions for Silvering Glass 265
C.1.5 Silvering of Telescope Mirrors in the Tropics 296
C.1.6 Recovery of Silver Waste Residues 297
C.1.6.1 Method 1 297
C.1.6.2 Method 2 299
C.1.7 The Deterioration of Silvered Glass Mirrors 300
C.1.8 Aluminizing Mirrors 302
C.1.8.1 Discussion 302
C.1.8.2 Application 306
C.1.9 Editor's Note 311
C.2 High-vacuum Equipment 315
C.2.1 General Description and Component Parts 316
C.2.2 Functional Characteristics 317
C.2.3 Mechanical Pumps 318
C.2.4 Diffusion Pumps 320
C.2.5 Valves and Manifolding 322
C.2.6 Baffles and Cold Traps 324
C.2.7 Gauges 325
C.2.8 The Vacuum Chamber 328
C.2.8.1 Geometry of the Vacuum Chamber 328
C.2.8.2 Heaters 329
C.2.8.3 Electrical Terminals 329
C.2.8.4 Optics Holders 329
C.2.8.5 Source Shields-Mechanical Motions 329
C.2.8.6 Glow Discharge-Electronic Bombardment 330
C.2.8.7 Filaments 331
C.2.8.7.1 Wire filaments: 331
C.2.8.7.2 Crucibles: 331
C.2.8.7.3 Refractory crucibles: 331
C.2.8.7.4 Tungsten "Boat'': 331
C.2.8.8 Assembly: 332
C.2.9 Electrical Supply 332
C.2.10 Notes on Processes and Operations 332
C.2.10.1 Outgassing 332
C.2.11 Evaporation of Metals 333
C.2.11.1 Aluminum Mirrors 333
C.2.11.2 Other Metals 334
C.2.11.3 Filament materials 336
C.2.12 Lens Coating 337
C.2.13 Interference Filters 339
C.2.14 Other Dielectric Films 339
C.2.15 Cleaning of Optics 339
C.2.16 Vacuum Leaks 340
C.2.17 Sputtering 340
C.2.18 Bibliography 341
C.2.19 Suggested Sources of Supply 344
C.2.19.1 Equipment 344
C.2.19.2 Mechanical pumps 345
C.2.19.3 Vacuum Valves 345
C.2.19.4 Gauges 345
C.2.19.5 Electrical Equipment 345
C.2.19.6 Materials and Supplies 346
C.2.20 About the Author 346
C.2.21 Notes Added in 1996 348
D The Eye and Atmosphere 351
D.1 Limitations of Vision with a Telescope 353
D.1.1 Resolving Power of the Eye 356
D.1.2 Astigmatic Eyes 358
D.1.3 Effect of Central Stops 358
D.1.4 Diameter of Eye Lens 359
D.2 Atmosphere, Telescope and Observer 361
D.2.1 The Atmosphere; its Currents 362
D.2.2 Different Kinds of Currents 365
D.2.3 Methods of Seeing the Waves 367
D.2.4 Features of Atmospheric Currents 368
D.2.5 Similar Phenomena 372
D.2.6 Causes of the Current Phenomena 373
D.2.6.1 Remarks upon the Floating Form 375
D.2.7 Effects of Currents on Seeing 376
D.2.8 The Telescope; Its Apertures 377
D.2.9 Eye-end Diaphragms 378
D.2.10 The Observer; Optical Qualities of the Eye 379
D.2.11 Contrast 381
D.2.12 Observer 383
D.2.13 Editor's Note 383
D.2.14 Double-star Separations for Estimating Image Motion 384
D.2.15 Note Added in 1996 385

E Other Optical Instruments 387
E.1 The Richest-Field Telescope 389
E.1.1 Editor's Note 389
E.1.2 Introduction 390
E.1.3 Further Notes 400
E.1.4 Editor's Note 405
E.1.5 Note Added in 1996 416
E.2 The Camera Obscura 419
E.2.1 Editor's Note 419
E.3 Maksutov Lens Applications 429
E.3.1 Mathematical Formulas 435
E.4 Metal Mirrors and Flats—a Composite Chapter 437
E.4.1 Editor's Note 437
E.4.2 Casting Speculum Metal 438
E.4.3 Allegheny Metal or Chrome Steel 439
E.4.4 Stainless Steel 440
E.5 Optical Systems for Astronomical Photography 447
E.5.1 The Reflector-Corrector 447
E.5.2 Two Photographic Lens Designs 467
E.6 How to Make a Cassegrainian (And Why Not To) 483
E.7 Cassegrainian and Gregorian Telescopes 489
E.7.1 Grinding and Polishing 493
E.7.2 Testing the Paraboloid 495
E.7.3 Testing the Secondary Mirrors 496
E.7.4 Practical Methods of Figuring Secondary Mirrors 498
E.7.5 Adjustments in the Telescope 500
E.7.6 Editor's Note 501
E.7.7 Additional Notes on the Hindle Test 503

F Instrumentation for Solar Observations 507
F.1 A Sun Telescope of 100-Foot Focal Length 509
F.2 A Simple Solar Telescope and Spectrohelioscope 513
F.2.1 Solar Telescope 513
F.2.2 The Spectrohelioscope 515
F.2.3 Editor's Note 523
F.2.4 Notes Added in 1996 523
F.3 A Spectroscope and Spectroheliograph 525
F.4 A Solar Spectroscope 537
F.4.1 A Solar Spectrograph 543
F.5 Building a Birefringent Polarizing Monochromator 547
F.5.1 Introduction 547
F.5.2 The Basic Filter 549
F.5.3 Optical Quartz 552
F.5.3.1 Sources of Quartz 552
F.5.4 Polaroid 556
F.5.5 Red Glass Filters 558
F.5.6 Tools of Construction and Use 559
F.5.6.1 Quartz Orientation 559
F.5.6.2 Grinding and Polishing 560
F.5.6.3 Mechanical Measuring Tools and Their Use 561
F.5.6.4 Spectroscopes and Their Use 562
F.5.6.5 Economy Measures 564
F.5.6.6 Optical Contacting 566
F.5.6.7 Calculations and Formulas 568
F.5.6.8 Required Accuracy 571
F.5.6.9 Cutting, Grinding and Polishing Quartz 577
F.5.6.10 Housing the Filter 580
F.5.6.11 Accessory Optics 582
F.5.6.12 Acknowledgement 585
F.5.7 References---Quartz-Polaroid Monochromator 586
F.6 The Interference Polarizing Monochromator 587
F.6.1 Optical Principles 588
F.6.2 Choice of Materials 590
F.6.3 Dimensions of the Plates 591
F.6.4 Making the Composite Prism 591
F.6.5 Use of the Monochromator 593