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The second edition of The Deep-sky Imaging Primer is a substantial update to the first edition, with revised and expanded text and over 325 illustrations. Printed in full color, it covers everything you need to know to capture stunning images of deep-sky objects with a DSLR or CCD camera:
- The fundamental concepts of imaging and their impact on the final image
- How to pick a telescope and camera
- How to get set up and take the images
- Where and when to find the best objects in the night sky
- How to process images using Adobe Photoshop® and PixInsight®
- Start-to-finish examples of image processing
Complete coverage of PixInsight® has been added, with workflows for both PixInsight and Photoshop®. There are also two new start-to-finish processing examples. The early chapters have been revised, with clearer explanations of important topics like noise and resolution. And a new appendix provides details of the best imaging targets for northern hemisphere imagers. Overall, it’s a bigger, more readable book, with a lot more content.
Like the first edition, the book is structured in three sections:
- Understanding Images explains how electronic sensors work and introduces the critical concepts of signal and noise.
- Acquiring Images describes how to use telescopes, cameras, and computers to capture deep-sky images.
- Processing Images is the longest section, covering everything you need to know to turn raw data from the camera into a deep-sky masterpiece. In addition to Adobe Photoshop, it now includes full coverage of PixInsight, which is fast becoming the main image processing tool for many imagers.
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Table of Contents Understanding Images
1 Electronic sensors The challenges of deep-sky imaging 8 How electronic sensors work 8 Well capacity and bit depth 9 The trade-off between dynamic range and gain 10 The importance of bit depth 11 Response curves and raw files 12 Creating color images 13 Sensor architecture 14 A CMOS revolution? 15 2 Signal and Noise A little statistics and quantum physics 16 Signal and noise at the pixel level 17 Shot Noise 18 An example of shot noise 20 A dimmer example 22 Skyglow 23 Thermal signal, hot pixels, and dark frames 24 Read noise and quantization noise 25 Variation in two-dimensions 26 Adding signals and noise 27 Acquiring Images
3 Mounts and Alignment Meridian flip 31 Polar alignment 32 Drift alignment 33 Tracking error 34 Balancing a mount 34 4 Cameras DSLRs 35 Dedicated astronomical cameras 35 Sensor size and pixel size 36 Connecting a camera to a telescope 37 5 Telescopes and optics Fundamental optical parameters 38 Telescopes for visual vs. imaging use 38 Optical aberrations 39 The Strehl Ratio 40 Refractors 40 Telephoto lenses 42 Reflectors and compound telescopes 43 Telescope quality 45 6 Image scale: matching sensor and optics Resolution and seeing 46 Sampling 47 The three constraints on resolution 48 Field of view 49 Equipment recommendations 50 Focal reducers and field flatteners 51 The ‘f-ratio myth’ debate 52 7 Choosing objects to image Getting a sense of scale 53 The deep-sky catalogs 53 Object types and the seasons 54 A survey of object sizes 57 Giant Objects (2° or greater) 57 Really Big Objects (1–2°) 58 Objects from 30–60' 58 Objects from 15–30' 58 Objects from 5–15' 58 Objects from 1–5' 58 Objects smaller than 1' 58 8 Focusing, guiding, and setting up Focusing 59 Achieving critical focus 59 Autoguiding fundamentals 60 Connecting computer to mount 62 Software and settings 63 Reducing setup time 64 Dovetails, rings, and other mount accessories 65 Power supplies 65 Dew prevention 66 USB cables and hubs 66 9 Filters and narrowband imaging Filters for imaging 67 Narrowband filters 67 Light pollution filters 69 DSLR filters and modification 70 10 Taking the exposures Controlling the camera 71 Choosing exposure duration and gain 71 Planning for a night of imaging 73 An image capture workflow 73 Dark frames 74 Flat frames 75 Bias frames 76 Dithering light frames 76 11 Atmospheric effects Light pollution 77 Target altitude 78 Local turbulence 79 12 Diagnosing problems and improving image quality Wind or tracking errors 80 Diffraction patterns 81 Flat fields 81 Focus 82 Halos 82 Tips for better images 83 Processing Images
13 Color in digital images Raw data and image file formats 85 Visual response to color 85 Color management and color spaces 87 LAB color 88 The HSL/HSV/HSB color model 88 White balance and color temperature 88 Deep-sky color accuracy 89 Color calibration with G2V stars 89 14 Calibration and stacking Calibration exposures 90 Throwing out problem shots 92 Stacking parameters 93 Calibration and stacking with DeepSkyStacker 94 The drizzle algorithm 97 Calibration and stacking with PixInsight 98 Creating a master bias in PixInsight 98 Creating the master dark and flat in PixInsight 99 Integrating light frames in PixInsight 101 Combining data from multiple nights 105 A PixInsight pre-processing cheat sheet 105 Using the BatchPreProcessing script 107 Diagnosing defects in calibration output 107 15 Principals and tools of post-processing PixInsight, Photoshop, or…? 108 Types of processing tools and a basic workflow 109 Selective adjustments 110 16 Processing images in PixInsight The PixInsight user interface 111 Working with images in PixInsight 112 Working with processes in PixInsight 115 Image and process containers 115 Saving the workspace as a project file 116 ScreenTransferFunction 116 A PixInsight post-processing workflow 117 17 Processing images in Photoshop Layers 119 Layer blending modes 120 Creating a composite layer 120 Selections and feathering 120 A Photoshop post-processing workflow 121 18 Using masks Masks in PixInsight 122 Creating a luminance mask with the RangeSelection process 123 Creating a star mask with StarMask 123 PixelMath 127 Using a uniform mask to moderate an effect 128 Masks in Photoshop 129 Creating a star mask in Photoshop 129 19 Color synthesis and gradient removal Aligning separate color channel images 131 Cropping out calibration artifacts 131 Aligning histograms with LinearFit 132 RGB color synthesis in PixInsight 132 RGB color synthesis in Photoshop 132 Narrowband mapped-color images 133 Correcting gradients 133 Gradient removal in PixInsight 134 Gradient removal in Photoshop 135 Color calibration in PixInsight 138 The PreviewAggregator Script 139 PixInsight’s PhotometricColorCalibration process 140 Combining luminance and RGB data in PixInsight 141 Combining luminance and RGB data in Photoshop 142 Creating a synthetic luminance image 142 20 Stretching: reallocating the dynamic range What is stretching? 144 Understanding the histogram 144 How different curves affect the histogram 146 Nonlinear transformation in PixInsight 148 Nonlinear transformation in Photoshop 149 Keeping the background neutral in Photoshop 150 Posterization: the perils of over-stretching 150 The effect of stretching on color 151 21 Noise reduction Visual noise, color, and scale 152 Noise reduction in PixInsight 153 Masking for noise reduction 153 An introduction to scale-based processing 153 MultiscaleMedianTransform 155 ACDNR 157 TGVDenoise 158 SCNR 159 Noise reduction in Photoshop 159 22 Adjusting color Enhancing color saturation in PixInsight 160 Enhancing color saturation in Photoshop 160 Narrowband color adjustments in PixInsight 162 Narrowband color adjustments in Photoshop 165 Mapping color in Photoshop with clipping layer masks 165 Correcting star color in narrowband images 166 Blending RGB star data into a narrowband image 167 Balancing Color in Photoshop 168 23 Contrast enhancement, sharpening, and deconvolution Creating contrast with S-curves 169 Object-background separation curves 169 Intra-object contrast curves 170 Local contrast enhancement in PixInsight 172 Dynamic range compression with HDRMultiscaleTransform 175 Local contrast enhancement in Photoshop with blend modes 175 Unsharp mask (Photoshop and PixInsight) 176 Photoshop’s HDR Toning tool 178 Photoshop’s high pass filter 179 Deconvolution vs. sharpening 180 Deconvolution in PixInsight 180 24 Star reduction and removal Reducing background star size 183 PixInsight’s MorphologicalTransformation tool 184 The minimum filter in Photoshop 186 Reducing the brightest stars 187 Star removal and separation in PixInsight 187 Star removal in Photoshop 190 25 Cosmetic repairs Cosmetic repairs in Photoshop 193 Correcting elongated stars 193 Cosmetic adjustments in PixInsight 194 26 Image composition Framing the scene 195 Orientation 196 Color 198 Step away from the computer 198 Images and reality 198 27 Plate solving and mosaics Plate solving and image annotation 199 Mosaics 200 28 A DSLR processing example 203 29 A CCD processing example 210 30 A Photoshop processing example 216 Exercise Answers 221 Moonlight Tables 224 Deep-sky Highlights 228 Index 233