Digital SLR Astrophotography

Half-title......Page 3
Title......Page 5
Copyright......Page 6
Dedication......Page 7
Contents......Page 9
Preface......Page 15
Part I Basics......Page 17
1.1 What is a DSLR?......Page 19
1.2.1 Major manufacturers......Page 22
1.2.2 Shopping strategy......Page 23
1.3 Choosing software......Page 24
1.3.3 Freeware......Page 25
1.4 Is a DSLR right for you?......Page 26
1.5 Is film dead yet?......Page 28
2.1.2 Raw vs. compressed files......Page 30
2.2 Focusing......Page 31
2.3.3 Dark-frame subtraction......Page 32
2.3.5 Grain......Page 33
2.5 Dust on the sensor......Page 35
2.7 No reciprocity failure......Page 37
2.8.1 The Bayer matrix......Page 38
2.9 Nebulae are blue or pink, not red......Page 39
3.1.2 Manual focusing......Page 42
3.1.4 White balance......Page 44
3.1.5 Do you want an automatic dark frame?......Page 45
3.1.7 Mirror vibration......Page 46
3.2 The camera as your logbook......Page 48
3.4.1 Things to set once and leave alone......Page 49
3.4.2 Settings for an astrophotography session......Page 50
3.5 Determining exposures......Page 51
3.6 Cool-down between long exposures......Page 52
4.1 Telephoto Moon......Page 54
4.2 Afocal Moon......Page 55
4.3 Stars from a fixed tripod......Page 56
4.4 Piggybacking......Page 60
4.5 Going further......Page 61
Part II Cameras, lenses, and telescopes......Page 63
5.1.1 Types of telescopes......Page 65
5.1.2 Types of coupling......Page 66
5.2 Fitting it all together......Page 69
5.3.1 Focal length......Page 71
5.3.3 f-ratio and image brightness......Page 72
What about stars and visual observing?......Page 73
5.3.4 Field of view......Page 74
5.3.5 Image scale in pixels......Page 76
5.4 Vignetting and edge-of-field quality......Page 77
6.1 Key concepts......Page 79
6.2 Optical calculations......Page 80
6.3.3 Meade f/3.3......Page 83
6.3.4 Others......Page 85
7.1.1 Big lens or small telescope?......Page 86
7.1.3 f-ratio......Page 87
7.1.4 Zoom or non-zoom?......Page 88
7.2.1 Sharpness, vignetting, distortion, and bokeh......Page 89
7.2.2 Reading MTF curves......Page 90
7.2.3 Telecentricity......Page 91
Canon......Page 92
7.3 Testing a lens......Page 93
7.4 Diffraction spikes around the stars......Page 94
7.5 Lens mount adapters......Page 96
7.5.1 Adapter quality......Page 97
7.5.2 The classic M42 lens mount......Page 98
7.6.1 How lens designs evolve......Page 100
7.6.2 The triplet and its descendants......Page 102
7.6.4 Telephoto and retrofocus lenses......Page 103
7.6.5 Macro lenses......Page 104
8.1.1 The viewfinder eyepiece......Page 105
8.1.2 The Canon Angle Finder C......Page 106
8.2.1 Confirmation by magnified playback......Page 108
8.3 Computer focusing......Page 110
8.4.1 Diffraction focusing......Page 111
In theory......Page 112
8.5 Focusing telescopes with moving mirrors......Page 114
9.1 Two ways to track the stars......Page 115
9.2 The rules have changed......Page 116
9.3.1 Using a wedge......Page 118
9.3.2 Finding the pole......Page 119
9.3.3 The drift method......Page 120
9.4.2 Must we make corrections?......Page 122
9.4.3 Guidescope or off-axis guider?......Page 123
9.4.4 Autoguiders......Page 124
9.5 How well can you do with an altazimuth mount?......Page 126
9.5.1 The rate of field rotation......Page 127
9.5.2 Success in altazimuth mode......Page 130
9.5.3 What field rotation is not......Page 131
10.1.1 The telescope......Page 132
10.1.3 Care of Li-ion batteries......Page 133
10.1.5 Safety......Page 134
Making a cable release for the Digital Rebel......Page 135
Customizing a cable release for higher-end Canons......Page 137
The USB link......Page 138
Parallel- and serial-port cables......Page 139
10.3 Networking everything together......Page 140
10.4 Operating at very low temperatures......Page 141
11.1 CCD and CMOS sensors......Page 143
Pixel size......Page 145
Color balance......Page 146
Effect of temperature......Page 147
Cosmic rays......Page 148
11.3.1 DSLR spectral response......Page 149
11.3.3 Is filter modification necessary?......Page 151
11.4.2 Interference filters......Page 154
11.4.4 Reflections......Page 157
Part III Digital image processing......Page 159
12.1 How to avoid all this work......Page 161
12.2 Processing from camera raw......Page 162
12.3 Detailed procedure with MaxDSLR......Page 163
12.3.1 Screen stretch......Page 164
Telling MaxDSLR about your dark frames......Page 165
Performing the subtraction......Page 166
12.3.3 Converting to color (de-Bayerization, demosaicing)......Page 167
How to align and stack......Page 170
12.3.5 Stretching and gamma correction......Page 171
Making screen stretch permanent......Page 172
Gamma correction......Page 173
12.3.6 Saving the result......Page 174
12.4 Processing from linear TIFFs......Page 175
12.4.1 Making linear TIFFs......Page 177
12.5 Processing from JPEG files or other camera output......Page 179
13.1.1 Bit depth......Page 181
13.2.1 TIFF......Page 182
13.3.1 Dots per inch......Page 183
13.3.3 The Drizzle algorithm......Page 184
13.4.2 Histogram equalization......Page 185
13.4.4 Gamma correction......Page 186
13.5.2 Unsharp masking......Page 188
13.5.4 Spatial frequency and wavelet transforms......Page 189
13.5.5 Deconvolution......Page 191
13.6.1 Gamut......Page 192
13.6.3 Color management......Page 193
Sum......Page 194
Average (mean)......Page 195
Median......Page 196
14.1.2 Stacking images in Photoshop......Page 197
14.2.2 Bias frames and scaling the dark frame......Page 199
Making the correction successfully......Page 201
14.3 Removing gradients and vignetting......Page 204
14.4 Removing grain and low-level noise......Page 205
14.5.1 Simple techniques......Page 206
14.5.2 Layer masking (Lodriguss' method)......Page 207
14.6 Other Photoshop techniques......Page 209
14.7 Where to learn more......Page 211
Part IV Appendices......Page 213
Appendix A Astrophotography with non-SLR digital cameras......Page 215
B.2 Using a webcam or video imager......Page 218
B.3 Using RegiStax......Page 222
Appendix C Digital processing of film images......Page 223
Index......Page 225