Table of Contents. vii

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1 Foreword iii Chapter 1 Introduction A Tour of Telescopes Getting Started Telescope Designs Auxiliary Optics Optics for Imaging Eyepieces Glossary and Bibliography Chapter 2 Visual Observing Structure of the Eye Optical Layout of the Eye Image Sensing in the Retina Properties of Human Vision Angular Resolving Power of the Eye Spectral Sensitivity of the Eye Brightness and Contrast Sensitivity of the Eye Properties of Human Vision Telescopic Observing with Eyepieces Exit Pupil Magnification Visual Telescopic Resolution Seeing Field of View Apparent Image Brightness Telescopes and Eyepieces for Visual Observing Telescopic Aperture for Visual Observing Telescopic Focal Ratio for Visual Observing Eyepiece Choices for Visual Observing Eyepiece Diameter and Field of View Image Sharpness in Eyepieces Chapter 3 Astronomical Imaging Imaging with CCD Sensor Arrays The Properties of Image Sensor Arrays vii

2 3.2.1 The Size of Image Sensor Arrays Spectral Sensitivity of Silicon Detectors Resolving Power of Sensor Arrays Noise in Image Sensor Arrays Image Sensor Demands on Optical Design Summary Chapter 4 Optics for Observers Light What is Optics? Optical Elements Lenses Plates Prisms Mirrors Optical Materials Optical Properties of Optical Materials Reflection from Optical Surfaces Physical Properties of Optical Materials Objects and Images Optical Ray Tracing Ray Tracing in a Nutshell Optical Coordinates and the Optical Axis Optical Prescription and Layout Meridional, and Tangential versus Sagittal Planes Longitudinal and Lateral Directions Surfaces Object Surface Optical Surfaces Stop Surfaces Image Surface Optical Systems First-Order Properties Rays Third-Order Properties: Aberrations Spherochromatism and Higher-Order Aberrations Correcting and Controlling Aberrations Petzval Curvature Vignetting Stray Light Wavefronts, Optical Path Differences, and Diffraction The Point Spread Function Exploring and Evaluating Optical Systems System Layout Optical Prescriptions viii Telescopes, Eyepieces, and Astrographs

3 4.9.3 Spot Diagrams Ray-Fan Plots Strehl Ratio Chapter 5 Achromatic Refractors Glass for Refractors The Refractor in Astronomical History, Part I A 100 mm Long-Focus Singlet Refractor Chromatic Aberration of a Singlet Analysis of the 100 mm ƒ/150 Singlet Lens Assessment of the 100 mm ƒ/150 Singlet Lens The Refractor in Astronomical History, Part II Achromatic Refractors Secondary Spectrum in Achromatic Doublets A 200 mm ƒ/15 Achromatic Airspaced Doublet Design of the 200 mm ƒ/15 Achromat Doublet Analysis of the 200 mm ƒ/15 Achromat Doublet Assessment of the 200 mm ƒ/15 Achromat Doublet Scaling Achromatic Doublets Chapter 6 Apochromatic Refractors What Exactly Does Apochromatic Mean? A 200 mm ƒ/15 Airspaced Apochromatic Doublet Design of the ƒ/15 Airspaced Apochromatic Doublet Analysis of the 200 mm ƒ/15 Airspaced Apochromatic Doublet Assessment of the 200 mm ƒ/15 Airspaced Apochromatic Doublet Three 200 mm Apochromatic Triplets Tertiary Spectrum in Apochromatic Triplets Design of the 200 mm Oiled Apochromatic Triplets Analysis of the 200 mm Oiled Apochromatic Triplets Assessment of the 200 mm Oiled Apochromatic Triplets A 200 mm ƒ/15 Super-Achromatic Triplet Design of the 200 mm ƒ/15 Super-Achromatic Triplet Analysis of the 200 mm ƒ/15 Super-Achromatic Triplet Assessment of the 200 mm ƒ/15 Super-Achromatic Triplet Three Smaller, Faster Apochromatic Refractors mm ƒ/9 Airspaced Fluorite Doublet mm ƒ/8 Oiled Fluor-Crown NPN Triplet mm ƒ/8 Airspaced Fluor-Crown NPN Triplet Thoughts on Refractors Chapter 7 Newtonian Reflectors The Story of the Newtonian Telescope The Newtonian Optical System How Much Coma? Formulas for Coma Blur Size Greg Smith, Roger Ceragioli and Richard Berry ix

4 7.4 The 200 mm ƒ/4.5 Newtonian Center-Field Performance of the 200 mm ƒ/4.5 Newtonian Wide-Field Performance at ƒ/ Further Analysis of the 200 mm ƒ/4.5 Newtonian Wide-Field Versus Narrow-Field Performance Newtonian Performance at ƒ/ Newtonian Performance at ƒ/ Center-Field Performance at ƒ/ Wide-Field Performance at ƒ/ Further Analysis of the 200 mm ƒ/8 Newtonian The ƒ/8 Newtonian as a Richest-Field Telescope Reflector Versus Refractor The Performance of Large-Aperture Newtonians Overall Assessment of the Newtonian Telescope Chapter 8 Cassegrain Telescopes A Brief History of Cassegrain Telescopes The Classical Cassegrain Telescope Cassegrain Central Obscuration Baffling in Cassegrain Telescopes The 200 mm ƒ/3 ƒ/ 8 Classical Cassegrain The 200 mm ƒ/4 ƒ/15 Classical Cassegrain The Dall-Kirkham Cassegrain The 200 mm ƒ/ 3 ƒ/ 8 Dall-Kirkham The 200 mm ƒ/4 ƒ/15 Dall-Kirkham The Ritchey-Chrétien Cassegrain The 200 mm ƒ/3 ƒ/8 Ritchey-Chrétien with a Curved Focal Surface The 200 mm ƒ/3 ƒ/8 Ritchey-Chrétien with a Flat Focal Surface A Cassegrain Caveat Chapter 9 Schmidt-Cassegrain Telescopes Genesis of the Schmidt-Cassegrain Telescope The Schmidt-Cassegrain Optical System Design Variables The Classic Schmidt-Cassegrain Telescope The 203 mm ƒ/2 ƒ/10 Classic SCT Analysis of the 203 mm ƒ/2 ƒ/10 Classic SCT Assessment of the 203 mm ƒ/2 ƒ/10 Classic SCT A 203 mm ƒ/3 ƒ/15 Spherical-Mirror SCT Analysis of the ƒ/3 ƒ/15 Spherical-Mirror SCT Assessment of the ƒ/3 ƒ/15 Spherical-Mirror SCT Coma-Free Schmidt-Cassegrain Telescopes A 203 mm ƒ/2 ƒ/10 Classic SCT, Respaced Analysis of the 203 mm ƒ/2 ƒ/10 Classic SCT, Respaced x Telescopes, Eyepieces, and Astrographs

5 9.7.2 Assessment of the 203 mm ƒ/2 ƒ/10 Classic SCT, Respaced A 203 mm ƒ/2 ƒ/10 Coma-Free SCT with an Aspheric Primary Analysis of the 203 mm ƒ/2 ƒ/10 Aspheric-Primary Coma-Free SCT Assessment of the 203 mm ƒ/2 ƒ/10 Aspheric-Primary Coma-Free SCT A 203 mm ƒ/2 ƒ/10 Aspheric-Secondary Coma-Free SCT Analysis of the 203 mm ƒ/2 ƒ/10 Aspheric-Secondary Coma-Free SCT Assessment of the 203 mm ƒ/2 ƒ/10 Aspheric-Secondary Coma-Free SCT Aplanatic Flat-Field Schmidt-Cassegrain Telescopes The 203 mm ƒ/2 ƒ/10 Aplanatic Flat-Field SCT Analysis of the 203 mm ƒ/2 ƒ/10 Aplanatic Flat-Field SCT Assessment of the 203 mm ƒ/2 ƒ/10 Aplanatic Flat-Field SCT Overall Assessment of Schmidt-Cassegrains Chapter 10 Maksutov-Cassegrains The Genesis of the Maksutov-Cassegrain A 200 mm ƒ/15 All-Spherical Gregory-Maksutov Analysis of the 200 mm ƒ/15 All-Spherical Gregory-Maksutov Assessment of the 200 mm ƒ/15 All-Spherical Gregory-Maksutov A 100 mm ƒ/15 All-Spherical Gregory-Maksutov Analysis of the 100 mm ƒ/15 All-Spherical Gregory-Maksutov Assessment of the 100 mm ƒ/15 All-Spherical Gregory-Maksutov Two Aspheric-Primary Maksutov-Cassegrains A 200mm ƒ/12 Retouched-Primary Maksutov-Cassegrain A 200 mm ƒ/12 Ellipsoidal-Primary Maksutov-Cassegrain A 200 mm ƒ/12 Rumak Analysis of the 200 mm ƒ/12 Rumak Assessment of the 200 mm ƒ/12 Rumak Overall Assessment of Maksutov-Cassegrain Telescopes Chapter 11 Cassegrain Telescopes with Sub-Aperture Correctors mm ƒ/3 ƒ/10 All-Spherical Catadioptric Klevtsov-Cassegrain Analysis of the 200 mm ƒ/3 ƒ/10 All-Spherical Klevtsov-Cassegrain Assessment of the 200 mm ƒ/3 ƒ/10 All-Spherical Klevtsov-Cassegrain Greg Smith, Roger Ceragioli and Richard Berry xi

6 mm ƒ/3 ƒ/10 All-Spherical Klevtsov-Cassegrain with Field Corrector Analysis of the 200 mm ƒ/3 ƒ/10 Klevtsov-Cassegrain with Field Corrector Assessment of the 200 mm ƒ/3 ƒ/10 Klevtsov-Cassegrain with Field Corrector Other All-Spherical Catadioptric Cassegrains with Secondary Corrector Assemblies mm ƒ/3 ƒ/8 Ritchey-Chrétien Cassegrain with Field Corrector Analysis of the 200 mm ƒ/3 ƒ/8 Ritchey-Chrétien Cassegrain with Field Corrector Assessment of the 200 mm ƒ/3 ƒ/8 Ritchey-Chrétien Cassegrain with Field Corrector mm ƒ/3 ƒ/6.8 Corrected Dall-Kirkham Cassegrain Analysis of the 508 mm ƒ/6.8 Corrected Dall-Kirkham Cassegrain Assessment of the 508 mm ƒ/6.8 Corrected Dall-Kirkham Cassegrain mm ƒ/7 Corrected Dall-Kirkham Cassegrain Analysis of the 305 mm ƒ/3 ƒ/7 Corrected Dall-Kirkham Cassegrain Assessment of the 305 mm ƒ/3 ƒ/7 Corrected Dall-Kirkham Cassegrain Overall Assessment of Cassegrain Telescopes with Sub-Aperture Correctors Chapter 12 Catadioptric Newtonians Two 200 mm Schmidt-Newtonian Telescopes Analysis of the 200 mm ƒ/4.5 Schmidt-Newtonian Analysis of the 200 mm ƒ/6 Schmidt-Newtonian Assessment of 200 mm ƒ/4.5 and ƒ/6 Schmidt-Newtonians Two 200 mm Maksutov-Newtonian Telescopes Analysis of the 200 mm ƒ/4.5 Maksutov-Newtonian Analysis of the 200 mm ƒ/6 Maksutov-Newtonian Assessment of 200 mm ƒ/4.5 and ƒ/6 Maksutov-Newtonians Assessment of Catadioptric Newtonians Chapter 13 Tilted-Component Telescopes Tilted-Component Optical Theory The Value of an Unobstructed Aperture The Historical Development of TCTs The Appearance of Two-Mirror TCTs Schupmann s Medial Telescope Anton Kutter and Post-WWII Developments Recent TCT Developments xii Telescopes, Eyepieces, and Astrographs

7 13.4 Analysis of TCT Designs All-Reflective TCT Designs The Anastigmatic Schiefspiegler Tri-Schiefspieglers The Yolo The Stevick-Paul Telescope and its Precursors Tetra-Schiefspieglers Reflective TCTs with Refractive Correctors The Catadioptric Schiefspiegler The CHiefspiegler Catadioptric TCT Designs The Super-Schupmann Medial Telescope The Hamiltonian-Schiefspiegler Chapter 14 Auxiliary Optical Modules: Focal Extenders, Coma Correctors, Focal Reducers, and Field Flatteners Three Focal Extenders Doublet Long Barlow Lens Triplet Shorty Barlow Lens Telecentric Barlow Lens Comparison of the Three Focal Extenders Coma Corrector for Newtonian Telescopes Design of the Coma Corrector for Newtonian Telescopes Analysis of the Coma Corrector for Newtonian Telescopes Assessment of the Coma Corrector for Newtonian Telescopes Focal Reducer Analysis of Focal Reducer Assessment of Focal Reducer Field Flattener for a Coma-Free Schmidt-Cassegrain Analysis of Field Flattener for a Coma-Free SCT Assessment of Field Flattener for a Coma-Free SCT Chapter 15 Refracting Astrographs The Origins of Astrophotography The Cooke Astrographic Triplet The 330 mm ƒ/5 Pluto Camera Cooke Triplet Analysis of the 330 mm ƒ/5 Pluto Camera Cooke Triplet Assessment of the 330 mm ƒ/5 Pluto Camera Cooke Triplet The 250 mm ƒ/5 Bruce Telescope Petzval Portrait Lens Analysis of the 250 mm ƒ/5 Bruce Telescope Petzval Astrograph Assessment of the 250 mm ƒ/5 Bruce Telescope Petzval Astrograph Later Professional Astrographs mm ƒ/5.5 Apochromatic Petzval Telescope Greg Smith, Roger Ceragioli and Richard Berry xiii

8 Analysis of 100 mm ƒ/5.5 Apochromatic Petzval Telescope Assessment of 100 mm ƒ/5.5 Apochromatic Petzval Telescope mm ƒ/8 Airspaced Apochromatic Triplet with Cemented Doublet Field Corrector Analysis of 150 mm ƒ/8 Apochromatic Triplet with Field Corrector Assessment of 150 mm ƒ/8 Apochromatic Triplet with Field Corrector Overview of Refracting Astrographs Chapter 16 Catadioptric Astrographs Optics for Imaging Schmidt Cameras Schmidt Camera Optics A 200 mm ƒ/2 Schmidt Camera Imaging Performance of the 200 mm ƒ/2 Schmidt Camera mm ƒ/5 Wright-Väisälä Camera Imaging Performance of the Wright-Väisälä Camera mm ƒ/4 Lurie-Houghton Astrograph Imaging Performance of the Lurie-Houghton Astrograph mm ƒ/3.3 Paraboloid with Wynne Corrector Imaging Performance of the Wynne-Corrector Astrograph mm ƒ/2 Hyperstar Astrograph Imaging Performance of the Hyperstar Astrograph mm ƒ/5 Maksutov-Cassegrain Astrograph mm ƒ/5 Schmidt-Cassegrain Astrograph mm ƒ/5 Corrected Dall-Kirkham Astrograph mm ƒ/3.5 Honders-Riccardi Astrograph Imaging Performance of the Riccardi-Honders Astrograph mm ƒ/8 Harmer-Wynne Astrograph Imaging Performance of the Harmer-Wynne Astrograph Summary Chapter 17 Eyepieces The Functions of the Eyepiece Pupils and Images Calculating Magnification Minimum Useful Magnification of an Eyepiece Working Focal Ratio of an Eyepiece Accommodation by the Observer s Eye Ray-Tracing Eyepieces Eyepiece Aberrations Assessing Eyepiece Performance Conditions of Use: Working Focal Ratio Conditions of Use: Eyepiece Focal Length xiv Telescopes, Eyepieces, and Astrographs

9 Conditions of Use: What Does the Observer Expect? Performance Criterion: Angular Blur Size Performance Criterion: Acceptable Wavefront Error Exploring Eyepiece Designs Narrow-Field Eyepiece Types (10 to 40 ) Kepler Eyepiece Galilean Eyepiece Huygens Eyepiece Ramsden Eyepiece Kellner Eyepiece Moderate-Field Eyepieces (30 to 45 ) Monocentric Eyepiece Abbe Orthoscopic Eyepiece Plössl Eyepiece Wide-Field Eyepieces (60 to 70 ) Erfle Eyepiece Zeiss New Field Glass Eyepiece Ultra-Wide-Field Eyepieces (80 to 110 ) Köhler s 110 Anastigmatic Eyepiece Nagler Eyepiece Ethos Eyepiece Eyepieces Compared Appendix A Understanding the Optical Prescriptions Found in this Book A mm ƒ/ 15 Achromatic Doublet Objective A mm ƒ/2 ƒ/10 Aspheric-Primary Coma-Free SCT A mm ƒ/4.5 Newtonian A.3.1 Coordinate Breaks Demystified A.4 150mm ƒ/12 Yolo TCT A mm ƒ/ 6 CHiefspiegler A mm ƒ/ 12 Super-Schupmann Medial A.7 10 mm Plössl Eyepiece A.8 10 mm Nagler-Type Eyepiece Glossary Bibliography Index Greg Smith, Roger Ceragioli and Richard Berry xv