Post on 09-Jun-2020
Optical Configurations for Astrophotography
Imaging the Sky 2012 Intel HF-3 Auditorium, Hillsboro, OR
May 5-6, 2012 Richard Berry
In this talk… I describe the designs commonly used by
amateurs, present a brief analysis of the performance that can be expected from a well-made instrument of each type, and discuss the
weaknesses and strengths of each design.
I do not discuss the merits of different manufacturers, but instead about the properties
of optical designs based on inescapable physical and optical limitations of their design.
Refracting Astrographs
• Achromatic Refractor • Apochromatic Refractor • Apochromatic Refractor w/ Field Corrector • Petzval Apochromatic Astrograph
Achromatic Refractor
Achromatic Refractor Color Curve
Achromatic Refractor Spot Matrix
Apochromatic Triplet 150mm aperture, ƒ/8
Apochromatic Triplet 150mm aperture, ƒ/8
Achromat versus Apochromat
Apochromatic Triplet w/ Field Corrector
150mm aperture, ƒ/8
Apochromatic Triplet w/ Field Corrector 150mm aperture, ƒ/8
Apochromatic Petzval Astrograph 100mm aperture, ƒ/5.5
Apochromatic Petzval Astrograph 100mm aperture, ƒ/5.5, at best visual focus
Apochromatic Petzval Astrograph 100mm aperture, ƒ/5.5, at best focus for imaging
Newtonian Reflectors
• The Basic Newtonian • Newtonian w/ Ross Coma Corrector • Paraboloid w/ Wynne Coma Corrector
Newtonian Reflector 200mm aperture, ƒ/4.5
Newtonian Reflector 200mm aperture, ƒ/4.5
Newtonian Reflector 200mm aperture, ƒ/4.5
Newtonian Reflector w/ Coma Corrector 250mm aperture, ƒ/4.5
Newtonian Reflector w/ Coma Corrector 250mm aperture, ƒ/4.5
Paraboloid with Wynne Corrector 300mm aperture, ƒ/3.3
Paraboloid with Wynne Corrector 300mm aperture, ƒ/3.3
Cassegrain Telescopes
• Classical Cassegrain • Ritchey-Chrétien Cassegrain • Ritchey-Chrétien w/ Focal Reducer
Classical Cassegrain ƒ/3 primary, ƒ/8 overall
Classical Cassegrain ƒ/3 primary, ƒ/8 overall
Ritchey-Chrétien Cassegrain ƒ/3 primary, ƒ/8 overall
Ritchey-Chrétien Cassegrain ƒ/3 primary, ƒ/8 overall
Ritchey-Chrétien Cassegrain ƒ/3 primary, ƒ/8 overall
Ritchey-Chretien Cassegrain w/ Focal Reducer 200mm aperture, ƒ/3 primary, ƒ/6 overall
Ritchey-Chretien Cassegrain w/ Focal Reducer 200mm aperture, ƒ/3 primary, ƒ/6 overall
Corrected Dall-Kirkham Cassegrain 300mm aperture, ƒ/3 primary, ƒ/7 overall
Corrected Dall-Kirkham Cassegrain 300mm aperture, ƒ/3 primary, ƒ/7 overall
Schmidt-Cassegrain Telescopes
• Classical SCT (has severe coma) • Coma-Free SCT (has field curvature) • Aplanatic SCT (wide, flat field) • Coma-Free SCT w/ Field Flattener • SCT w/ Hyperstar module (very fast)
Classical Schmidt-Cassegrain ƒ/2 primary, ƒ/10 overall
Classical Schmidt-Cassegrain ƒ/2 primary, ƒ/10 overall
Coma-Free Schmidt-Cassegrain ƒ/2 primary, ƒ/10 overall
Coma-Free Schmidt-Cassegrain ƒ/2 primary, ƒ/10 overall
Coma-Free Schmidt-Cassegrain ƒ/2 primary, ƒ/10 overall
Coma-Free Schmidt-Cassegrain w/ Field Flattener 200mm aperture, ƒ/2 primary, ƒ/10 overall
Coma-Free Schmidt-Cassegrain w/ Field Flattener 200mm aperture, ƒ/2 primary, ƒ/10 overall
Aplanatic Schmidt-Cassegrain ƒ/2 primary, ƒ/10 overall
Aplanatic Schmidt-Cassegrain ƒ/2 primary, ƒ/10 overall
Aplanatic Schmidt-Cassegrain ƒ/2 primary, ƒ/10 overall
Schmidt-Cassegrain Telescopes Coma-Free versus Aplanatic
Hyperstar Astrographic Module 280mm aperture, ƒ/2 primary,ƒ/2 overall
Hyperstar Astrographic Module 280mm aperture, ƒ/2 primary,ƒ/2 overall
Heavy-Duty* Astrographic Cameras
• Maksutov-Cassegrain • Schmidt-Cassegrain • Corrected Dall-Kirkham Cassegrain • Riccardi-Honders Astrograph • Harmer-Wynne Astrograph
* aperture > 300mm, wide-field, short focus
Maksutov-Cassegrain Astrograph 300mm aperture, ƒ/5 overall
Maksutov-Cassegrain Astrograph 300mm aperture, ƒ/5 overall
Schmidt-Cassegrain Astrograph 300mm aperture, ƒ/5 overall
Schmidt-Cassegrain Astrograph 300mm aperture, ƒ/5 overall
Corrected Dall-Kirkham Astrograph 300mm aperture, ƒ/5 overall
Corrected Dall-Kirkham Astrograph 300mm aperture, ƒ/5 overall
Riccardi-Honders Astrograph 300mm aperture, ƒ/3.5 overall
Riccardi-Honders Astrograph 300mm aperture, ƒ/3.5 overall
Harmer-Wynne Astrograph (“Hyperion”) 315mm aperture, ƒ/8 overall
Harmer-Wynne Astrograph (“Hyperion”) 315mm aperture, ƒ/8 overall
Optical Configurations for Astrophotography
Imaging the Sky 2012 Intel HF-3 Auditorium, Hillsboro, OR
May 5-6, 2012 Richard Berry