Learn Photo Editing

Learn Photo Editing

This online course gives professional advice and instructions for how to photoshop pictures for any purpose that you could need them for. If you need to retouch your portraits, this gives you the tools to edit the image so that your model is sure to be happy with the results. If you need to create cartoon characters, you can learn how to do that in a very short amount of time. You can even learn the more advanced skills, like how to make facial features stand out in the picture without having to retouch the photo. You can learn how to take your normal photos and turn them into glossy, high resolution advertisements. Whatever skills you want to learn, and whatever application your photos will be needed in, this course can give you the tools that you need in order to create the most beautiful photoshoot that you've ever done. Read more...

Learn Photo Editing Overview


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Highly Recommended

The author presents a well detailed summery of the major headings. As a professional in this field, I must say that the points shared in this ebook are precise.

When compared to other e-books and paper publications I have read, I consider this to be the bible for this topic. Get this and you will never regret the decision.

Astronomical image processing

As an alternative to MaxDSLR I also use Nebulosity (from www.stark-labs.com). This is a quick and simple image processing package for DSLR users, similar in overall design to MaxDSLR but much lower priced. (The two make a good pair.) Like MaxDSLR, Nebulosity not only processes images, but also controls the camera in the field. It runs on the Macintosh as well as the PC.

Methods Of Sxt Image Processing And Analysis

From the earlier analysis of the best high resolution flare X-ray images (Herant et al. 1991) and results of theoretical considerations (Gomez, Martens, & Golub 1993) it follows that the structuring and most of physical processes operating in solar flares act on small sub-arcsecond scales, i.e. below the nominal resolution of SXT images on Yohkoh. As the SXT pixel dimension and the FWHM of the point spread function (PSF) of the grazing incidence mirror are of similar sizes it is then possible to increase the effective resolution of the images by using image reconstruction techniques. A number of methods have been worked out and presented in the literature which allow the instrumental blurring to be removed. However, there was no well documented method (except the work of Roumeliotis 1995) which allows deblurring and over sampling to be performed simultaneously. Oversampling means that the recovered (deconvolved) picture contains more resolution elements than the original one. In...

Overview of image processing

Digital image processing is a big subject, and I don't plan to cover all of it here. In particular, in this and the following chapters I'm going to skip almost all of the mathematics. To learn how the computations are actually done, see Astrophotographyfor the Amateur (1999), Chapter 12, and other reference books listed on p. 195. This is also not a software manual. For concreteness, I'm going to give some specific procedures for using MaxDSLR (including its big brother MaxIm DL) and, in the next chapter, Adobe Photoshop, but in general, it's up the makers of software to tell you how to use it. My job is to help you understand what you're trying to accomplish. Many different software packages will do the same job equally well, and new software is coming out every day.

B61 Image Processing Books General

Digital Image Processing Principles and Applications. New York John Wiley & Sons, 1994. An easy-to-read, largely non-mathematical introduction to image processing, with lots of examples and pictures. Includes a diskette with simple demonstration program. Castleman, Kenneth R. Digital Image Processing. Upper Saddle River, NJ Prentice Hall, 1996. Intended as a textbook, this book offers a comprehensive view of image processing. The discussions of the histogram, point and linear operators, and filtering in the Fourier domain are especially comprehensible. Gonzales, Rafael, and Paul Wintz. Digital Image Processing. 2nd ed. Reading, MA Addison-Wesley, 1987. This volume is an update of the classic work in image processing, usually referred to by the authors' names alone Wintz and Gonzales. The text moves rapidly through the basics to focus on processing and enhancement in frequency space. Jahne, Bernd. Digital Image Processing. Berlin Springer-Verlag, 1991. Every author...

B62 Image Processing Science Applications

Digital Image Processing A Systems Approach. 2nd ed. New York Van Nostrand Reinhold, 1989. The focus of this book is image processing as applied to spacecraft imaging. Includes examples from Landsat, Voyager, and Viking. The discussions of computer hardware are long out of date. Jahne, Bernd. Practical Handbook on Image Processing for Scientific Applications. Boca Raton CRC Press, 1997. Focuses on image acquisition and analysis for scientific research. Full of useful hints for programmers. Russ, John C. The Image Processing Handbook. 2nd. ed. Boca Raton CRC Press, 1994. Probably the most comprehensive non-mathematical work on image processing in science applications in fields like materials science and biology, but an excellent source of ideas for astronomy. Heavily illustrated. Sanchez, Julio, and Maria P. Canton. Space Image Processing. Boca Raton CRC Press, 1998. This book is about the acquisition and processing of images from spacecraft, with a primary focus on...

B66 Image Processing Algorithms

High Performance Computer Imaging. Greenwich, CT Manning, 1996. Covers all basic topics in image processing from the standpoint of a programmer looking for efficient ways to code them. Klette, Richard, and Piero Zamoeroni. Handbook of Image Processing Operators. Chichester John Wiley and Sons, 1996. Describes dozens of operators, with algorithms and sample code in Pascal. Well worth reading for the practical programmer. Pavlidis, Theo. Algorithms for Graphics and Image Processing. Rockville MD Computer Science Press, 1982. A fascinating look at image processing from a pioneer in the field includes instruction for printing gray scale images by multiple character strikes on a line printer Solid material despite its age. Schwaderer, W. David. Digital Imaging in C and the World Wide Web. Wordware Publishing, 1998. Covers a broad range of basic image processing, with a good section on color models. Includes a chapter on the social issues raised by altering digital images....

Basic Image Processing

Let me come clean before we even begin this Chapter - I am not an image-processing expert, in fact I just about get by. However, what you will learn from this section of the book should provide you with the basis of getting some very good-looking results from your hard won data. I will also give you the process by which I transform the raw FITS data into a file ready for image processing. This procedure is by no means meant to be definitive. I have found that it works well for me, but I am sure that there are better procedures to follow, and better ways of processing your images. There is however one very important observation I have made that should help you in getting the best out of your data and it is this there is no set processing sequence that you can apply for all your images You must treat every image as unique and worthy of its own special attention, because it is unique. The noise characteristics will be different from any other image you take, the background signal will be...

C92 Multi Image Processing

With the Multi-Image feature, AIP4Win provides you with the ability to process a whole night's worth of images automatically. Multi-Image processing is performed similarly to the Track & Stack processing. Instead of selecting the Stack process type, if you select Individual Files, the images will be calibrated and saved to separate files instead of being summed together. The Auto-Process Tool provides a set of the same basic image enhancement functions we used in the Image Enhancement tutorial, and they can be applied automatically to each image. When you choose individual image processing, you are presented with the ability to choose a format to save your images, and to select where they are saved.

B67 Image Processing Software

By Software Bisque (Tom and Steve Bisque). Windows PC-based, commercial. CCDSoft is an astronomical image processing and CCD image acquisition program that supports the full line of SBIG CCD camera and Apogee Instruments cameras. Written and tested by experienced astronomers, CCDSoft combines power with ease of use. By using CCDSoft in conjunction with TheSky, you can control both computer-driven telescopes and CCD cameras from your computer, creating an unmatched system for astronomical observations. Info http www.bisque.com. CCD Image Processing. By Frank Jan Sorenson. Windows PC-based shareware, Cookbook oriented. Info http.V home4.inet.tele.dk frank.s ccdprog.html. Images Plus. By Mike Unsold. Windows-based general-purpose image processing software, featuring support for digital SLR cameras. 4193 Tallmadge Road, Rootstown, OH 44272 (330) 325-0765 www.mlunsold.com. Maxim DL. By Cyanogen Productions, Inc. Windows PC-based, commercial. Maxim DL includes a variety of image...

Image Processing with Photoshop

With Adobe Photoshop you can sharpen the image's lightness channel after wavelet sharpening in RegiStax. Lightness channel sharpening does a good job of sharpening the image without causing color artifacts. There are three steps to this process. First, convert the image to Lab colors. Next, in Channels, select only the lightness channel and do an unsharp mask on it. Finally, convert the image back to RGB colors. The Moon's limb and image noise will determine the strength of lightness channel sharpening.

Creating the Image Processing File

You have finished your image session and you have brought the valuable sub-exposure data indoors to be processed into a wondrous deep-sky image. There are a number of hurdles to be overcome before we end up with a pretty picture. The first thing to do is to convert your individual FITS sub-exposures into IEEE floating point format using Maxim DL's Batch Save and Convert routine. This step is not entirely necessary if you do not have the software to carry out the conversion. You now need to convert the files to colour RGB files. Assuming you have the SXV-H9C (or similar) one-shot colour camera, you run the Convert RGB function as a batch conversion using the Command Sequence Window. The Command Sequence Window allows you to convert all your subs into RGB frames using the Convert RGB command. For the SXV-H9C camera you need to have both the X-offset and the Y-offset boxes ticked in the Convert RGB dialog, you will also use the High Quality deBayer mode. If you are using the SXVF-M25C...

Astronomical Image Processing Software

Ble to clearly see what is trying to be communicated, then the vocabulary might be insufficient. While astronomical image processing software might seem to be strictly in the domain of those fortunate enough to have a CCD camera, in fact there are many uses for such software. For example, a broad selection of CD-ROMs containing raw image data from the Voyager flights through the outer Solar System are available, and image processing software can reveal an absolute wealth of information and allow even the novice to view previously unpublished images from this material. Other sources of raw astronomical image data exist on the Internet, and this material can be analyzed and processed by anyone willing to take the time to download the material. While several of the Swiss Army Knife planetarium software programs include limited image processing facilities, none offer the depth of features and capabilities of the stand-alone applications discussed here. AstroArt (Fabio Cavicchio, msb...

Image Processing

Image-processing software enhances image details (Figures 2.11 and 2.12). How you view the image affects how you process it. For example, if you display your image on the Web, the image needs to be smaller than about 800 x 600 pixels to be Web site-friendly. This allows the complete image to be displayed on most computer monitors without scrolling. If you want to print the image, then process the image to have a resolution of 240 to 300 dpi and adjust the image to be brighter in the dark areas than a Web image because most printers will not print details in the very dark areas. When sharpening the Moon, watch carefully for oversharpening and creating a bright edge at the limb. Cor Berrevoets' RegiStax (aberrator.astronomy.net regis-tax) wavelet image processing does a good job sharpening the image.

Photo editing

For general-purpose photo editing, the software that comes with your camera may be adequate, especially if you pair it up with relatively powerful astronomy software. What you need is the ability to crop and resize pictures, adjust contrast and color balance, and make prints. The king of the photo editors is of course Adobe Photoshop, which is one of the basic tools of computer graphics many scientific add-ons for it have been developed. But Photoshop isn't cheap. An alternative is Photoshop Elements, which may even come with your DSLR this is a cut-down version of Photoshop that does not process 16-bit TIFFs but is otherwise satisfactory. Or you can use its leading competitor, Corel's Paint Shop Pro (www.corel.com). Note that there are often upgrade discounts for people moving to Photoshop from Photoshop Elements or from competitors' products.

Adobe Photoshop

What a program You could continue to learn about the nuances until the cows come home. There is such an enormous volume of tools to extract that extra miniscule piece of latent information from the image you have taken that the learning curve is endless. All I propose to do is to run through the basic routine that I adopt in processing an image. There is so very much more that the expert will do in fine tuning his or her image. If you want to get technical I recommend Photoshop Astronomy by R. Scott Ireland. This is an in-depth look at the application of Photoshop tools for astronomical imaging. Now back to mere mortals To demonstrate the effect of various tools, Fig. 8.5 shows a wide field image centered on NGC 7822 in Cassiopeia, downloaded into Photoshop and adjusted in levels. Figures 8.6-8.8 show further adjustments. Now that the luminance image is complete the hard work starts. I usually assemble the filtered color images in both Maxim and...

C7 Image Enhancement

This tutorial demonstrates a few of the image enhancement tools in AIP4Win. In it and those that follow, you will learn how to use these tools to extract detail from otherwise bland images. More than just producing pretty pictures, these techniques can be used to enhance details and show structures that, because of their low contrast, would otherwise be invisible. Later tutorials show you which tools and processes to use on deep-sky and planetary images.

Preface to the First Edition Jims Remarks

I first became seriously interested in image processing in the late '80s. I was working at Bell Labs at the time and had access to a lot of interesting people and computer resources. I remember playing with the Voyager images as they became available. During lunch and after hours, my buddies and I would experiment to see what we could do with them. I used an image-processing tool called IMDISP, written by Ron Baalke, and available via an ftp site at NASA. A bunch of us used to pass the images around on the old USENET, and it was fascinating to see what details we could coax out of the amazing data coming back from Jupiter, Saturn, Uranus and Neptune. This was in the pre-Hubble days, and there was very little deep-sky imagery available over the internet at that time when someone found a place where you could download images of nebulae and galaxies, it was usually very slow because of all the people downloading the images. The next spring my buddy Neil and I built our first Cookbook 245...

Preface to the Second Edition

We are proud to present a new edition of the Handbook of Astronomical Image Processing to our readers. As anyone who has participated in the rapidly evolving field of astronomical imaging already knows, everything has changed. New hardware and new software tools have emerged, computers are faster, and the Internet has become more inclusive. Yet underneath it all, the fundamentals remain the same. On clear nights we wait as a trickle of photons enters the telescope, strikes the detector, and accumulates into an image of a distant place in the cosmos.

Nonconforming FITS Files

Another variation on the theme is using valid keywords in a way that does not tell the software how to interpret the data array. Suppose that the DAT AM IN and DATAMAX keywords appear in the header, with DAT AM IN -32768.0 and DATAMAX 32767.0. The programmer probably hoped that the FITS reading program would deduce the necessary offset and scale the data array values correctly. But DAT AM IN and DATAMAX were not intended to function in this way they specify only the range of pixel values that the image processing software will find in the data. They say nothing about how the data should be read or interpreted.

Non Linear Enhancement Operators

The human eye and brain are such powerful image processing tools that it is difficult to find operators that perform functions that a human being cannot do more easily. However, two non-linear operators stand out from the crowd of candidates the extreme value operator, and local adaptive sharpening.

Color in Color Images

Figure 21.12 Case study Luminance-channel processing opens color images to a wide variety of powerful image-processing functions. On left is the original image of the Orion Nebula, and on the right is same image enhanced with wavelet spatial filtering to sharpen and heighten nebular details. Figure 21.12 Case study Luminance-channel processing opens color images to a wide variety of powerful image-processing functions. On left is the original image of the Orion Nebula, and on the right is same image enhanced with wavelet spatial filtering to sharpen and heighten nebular details. Color balance is just the beginning for color image processing. In color images from digital cameras, the luminance channel always has a higher signal-to-noise ratio than chrominance channels do enabling you to apply powerful image processing routines to the luminance channel. And because changes to the luminance channel don't alter the color balance, you can experiment freely.

B11 CCD Imaging Books

Choosing and Using a CCD Camera. Richmond, VA Will-mann-Bell, Inc., 1992. This book's subtitle, A practical guide to getting maximum performance from your CCD camera, describes its mission well. Written as an introductory guide for amateur astronomers, it presents topics such as field of view, calibration, integration time, guiding, tracking, and image processing in a digestible format. McLean, Ian. Electronic Imaging in Astronomy, Detectors and Instrumentation. Chichester John Wiley and Sons, 1997. Although it was written by a professional astronomer for professional astronomers and graduate students, this book will interest students at all levels as well as amateurs who are serious about astronomical imaging. Comprehensive discussion of topics from the physics of CCD detectors through telescopes and instrumentation to computers and image processing.

C77 Morphological Processing

Morphological processes are not the usual stock-in-trade of astronomical image processing, but some of them do have their uses from time to time. AIP4Win provides a whole suite of these functions, the most useful of which are the feature-detection operators. In this tutorial, we will explore several of those functions. However, the Contour Map is probably the most fun. Our test image shows the Whirlpool Galaxy, M51. Step 1 Load the Image. Load the image file m51.fts from the Image Enhancement subdirectory of the Tutorial directory on the CD-ROM. Check the Auto button on the Image Display Control to make sure the image is fully stretched.

About this book and software

This second edition of the Handbook of Astronomical Image Processing (HAIP) and its integral AIP for Windows 2.0 image processing software (AIP4Win 2.0) addresses many important changes that have taken place in astronomical imaging since the publication of the first edition. Today's affordable astro-imaging capable digital single-lens-reflex (DSLR) cameras, the growing power of personal computers, and the proliferation of telescopes and imaging accessories has brought imaging capabilities within the reach of practically every amateur astronomer and this second edition of the Handbook plus AIP4Win 2.0 is ready, willing and able to assist every observer in making great astronomical images. AIP4Win 2.0 now has the ability to perform wavelet image enhancement, wavelet image analysis and wavelet noise reduction techniques so new they're not even mentioned in the classic works about image processing. The deconvolution procedures have been enhanced so not only do they run faster than ever...

C71 Brightness Scaling

This is the most basic of image enhancement functions, and is the most frequently Astronomical Image Processing for Windows Figure C.9 Changing the value of pixels is the first and foremost technique used in astronomical image processing. Shown above, the Histogram Shaping tool modifies pixel values in the Eagle Nebula image to reveal both the dim glowing cloud of gas and the bright star cluster at its core. Step 1 Load an Image. To make the results of this tutorial more visible, we are going to set the default image stretch mode to Black White Stretch. You do this by selecting the Black White Stretch button on the Defaults tab of the Image Display Control. (You will need to load an image first, in order for this window to come up.) Make sure that the Black White Stretch values are set to 0 and 65535. First load the image file ml6.fts from the Image Enhancement subdirectory of the Tutorial directory on the CD-ROM. When the image loads, click the Default B W button on the Image Display...

Limited Warranty Statement

Also new is a suite of editing functions to fix bloated star images, patch image flaws, and smooth bothersome sky gradients along with an image display control that helps you visualize all the information - and beauty - contained in your digital images. In short, AIP4Win 2.0 is a full-featured image-processing program designed and optimized for loading, processing and displaying astronomical images. Here are a few of its capabilities When you purchase the Handbook of Astronomical Image Processing, you receive one CDROM containing AIP4Win 2.0 that is licensed for use on one personal and a portable computer if you own one. This software requires validation via the web (or telephone) within 30 days of installation. Once validated, you also receive the right to updates (free downloads via the web) and upgrades (for a fee) as they become available. You agree not to give or sell copies of AIP4Win 2.0 to others because you understand that, with our low...

C8 Fast Fourier Transform

AIP4Win implements one of the most powerful of all image processing tools spatial filtering. The Fast Fourier Transform (FFT), the basic process behind most spatial processing, is covered in Chapter 17. Before running this tutorial, read this chapter to gain an understanding of spatial filtering. Step 8 Try a Real Image. Open the 030119204.ccd image from the Image Enhancement tutorial directory. Invoke the Auto FFT Tool and set it up as follows

When you are finished close all the open images C73 Convolution Filtering

From the Image Enhancement Tutorial subdirectory, load the image moon.pa. This is an image taken with a Cookbook 245 CCD camera through a telescope with a tiny 6-millimeter aperture, so the image appears rather soft. We will use this image later with some more powerful techniques.

Exploring Frequency Space

Spatial Fence

The fundamental idea behind frequency-domain image processing is that every image can be decomposed into a unique spectrum of spatial frequencies. We can apply this concept by altering the spectrum and then transforming it back to a new image that has changed characteristics. With appropriate alterations to the spectrum, we can enhance image detail, alter the energy distribution in the image, and remove noise just to name a few of the many applications.

TIFF The Standard in the Graphic Arts

TIFF is the image file format preferred in the graphic arts industry. Photo-editing software, paint programs, and desktop-publishing applications use TIFF because it is a powerful and flexible image format. However, this very flexibility is sometimes the undoing of TIFF. This standard supports black-and-white binary images, 8-bit grayscale images, 8-bit palette color images, 16-bit RGB color images, 24bit RGB color images, as well as specialized graphics needs such as 32-bit CMYK color. TIFF files can be written in the PC's Intel little-endian byte order as well as Apple's Motorola big-endian byte order. TIFF even supports data in floating-point format, and allows proprietary data formats. In addition, the image data can be uncompressed, or it can be compressed using run-length-limited (RLE), Lemple-Ziv-Welch (LZW), or JPEG compression. Expecting one program to read every possible type of TIFF file is asking a great deal

Properties of Color Images

Jpeg Compression Noise

To determine how to obtain excellent results from digital camera color image files, we will begin by examining their distinctive properties. (In Chapter 7, we performed a similar analysis for astronomical CCD cameras.) Our goal in this examination is to develop image-processing techniques to exploit the embedded color information while offsetting and overcoming undesirable artifacts. Film Grain in Scanned Images. Scanning films and prints is an effective way to bring older images into an image-processing environment. However, in addition to a small amount of digital noise from the linear CCD array in the scanner, you can expect film grain. Unlike the statistical variations due to photon noise where the variation in a pixel is independent of adjacent pixels, film-grain noise is correlated from one pixel to the next. Correlated noise of this type is extremely difficult to filter out, and almost always represents the limiting factor in enhancing scanned film images. Like their CCD...

C76 Wavelet Spatial Filtering

One of the most exciting image processing technologies to come along in recent years is wavelet processing. AIP4Wiri s Wavelet Spatial Filter provides unique capabilities for image enhancement not matched by other processing techniques. To get the most out of this tutorial it is recommended that you read Chapter 18, so you will have a better idea of what is happening, as well as a better understanding of the terminology. Step 1 Load an image. Load the image IC5070HaStack.fts from the Image Enhancement tutorial subdirectory. This image is a Hydrogen-alpha filtered image of the Pelican Nebula. (The pelican namesake is recognizable if you use the Transform Translate-Rotate-Scale tool to perform a quick 90 degree counterclockwise rotation of the image. Try it and see.)

Processing Color Images

Digital cameras, webcams, and Bayer-matrix astronomical CCD cameras capture color images directly, and after scanning, negatives and photographic prints provide a further source of images that can almost certainly benefit from digital image processing. In this chapter, we examine what to expect in digital color images, how to collect good color images, and how to process color images We begin by examining the properties of color images to see how these set them apart from the monochrome FITS images generated by astronomical CCD cameras. Next, we discuss basic calibration techniques (dark subtraction and flat-fielding) that can often improve image quality, and then combine multiple exposures (a process called stacking) to build an image with a high signal-to-noise ratio. Finally, we cover methods of representing color images inside your computer and how these effect color balance and image enhancements such as sharpening, deconvolution, and wavelet sharpening.

Jims Remarks

The imaging hardware is not the only thing that has changed. Computer hardware, following Moore's Law, has steadily improved its capabilities to the point where an 80-gigabyte hard drive and 500 megabytes of RAM are found even on entry level systems. This gives the software developer much more freedom to implement numerically intensive image processing routines without the problem of them taking all night to execute. The art of image processing has undergone continuous growth as well, with The software, originally written with a 486 PC having 16MB of memory and an 800x600 display as a minimum system, has been rewritten to take advantage of the current crop of entry level PCs with multi-GHz CPUs and hundreds of megabytes of main memory. This new crop of PCs allows routines to be written which were just too computation-intensive to be implemented before. More experience in using the tools in the hands of so many talented imagers has provided tremendous feedback on the techniques and...

Linear Operators

Among the most useful tools in the image-processing repertoire are those that generate a new pixel value based on the relationship between the value of a given pixel and the values of those that surround it. This chapter and the next describe image processing with neighborhood operations that is, processes that involve the pixel's immediate (and not-so-immediate) neighbors.

C14 Conclusion

These tutorials barely scratch the surface of AIP4 Win's capabilities. Experiment with the tools to get familiar with them and what they can do for your images. You will soon learn that no one tool does everything, and that the real power in image processing lies in learning how to use tools together.

Appendix C Tutorials

We have written these tutorials to help you master the AIP4Win image-processing software program included with this book. Each tutorial walks you through activities designed to clarify and reinforce the concepts that you have learned in the book. For the best learning experience, we recommend that you first follow each tutorial exactly as we have written it. Then repeat the tutorial while experimenting and trying out new processing variations using your own CCD images. We find the best way to use these tutorials is to run AIP4Win on your computer as you follow the instructions in the book. You will find test images on the accompanying CD-ROM in the Tutorials directory. Each tutorial covers a specific set of program features and builds a specific set of image-processing skills and, of course, each builds on the skills you have acquired in the previous ones. The tutorials are listed in Table C.l. Before You Start remember that AIP4Win is unique. It is a program conceived, designed, and...

Fourier Theory

The mathematical theory that Fourier introduced in 1822 was a long way from modern digital image processing. In this section, we examine the four steps that lead from his original series summation to the fast Fourier transform used in image processing the Fourier series, the Fourier integral, the discrete Fourier series, and the fast Fourier transform. Our goal is not to teach you the math, but to show the chain of reasoning that underlies the Fourier transform. Although these equations apply to one-dimensional functions, it is possible to develop equations for two-dimensional functions that is, for images. In image processing, we transform an image into frequency space, modify its frequency content, and then apply the inverse transform to recover the modified image.

Richards Remarks

Nine years have passed since Introduction to Astronomical Image Processing, the forerunner of this book, appeared. In its preface, I wrote Today, my dream has come true and that is why I wanted to write this book. This is a book about images and manipulating images extracting data, seeing the unseen, enhancing detail until the raw information collected at the telescope has yielded everything there is to see and know. I wanted this book to be a behind-the-scenes look at image processing not another drag this and click that computer book, but an in-depth analysis and exploration of how image processing works. I wanted a book that wasn't afraid to dig into the math and show you the algorithms that image processing software uses to measure and manipulate images. For me, writing the Introduction to Astronomical Image Processing was a splendid opportunity to learn the basics of image processing. The book included a tidy little processing program AIP, alias AstroIP that I had written to...

C11 Deep Sky Images

Up to this point, the tutorials have been focussed on specific features of AIP4Win. This and the following tutorial demonstrate using a group of AIP4Win functions to solve typical image processing challenges. This tutorial focuses on enhancing deep-sky images. Another thing you will notice about the image is the artifacts along the top and left edges due to the stacking process. The scope drifted about 10 pixels to the right and about 10 pixels down between the first and last exposure. This left an area along these two edges that does not contain contributions from all of the images. The pixel values encountered in these regions throw off the statistics for the image and can often cause the Auto-Stretch function to display it incorrectly. It will also affect image enhancement tools that rely on image statistics to do their jobs. You will usually want to crop these edges.

Image Registration

Two images are said to be in register when corresponding features appear at the same pixel coordinates. Stars are ideal reference points for images, because they are both plentiful and fixed in space but virtually any well-defined image feature can be used as a reference point. For precise registration, the image processing software must be able to compute a centroid for each reference point, under good conditions, to better than 0.05 of a pixel.


Wavelets are a relatively recent invention, a hybrid between the spatial methods of operators and kernels, and the frequency-based methods of the Fourier Transform. In many ways wavelet image processing offers the best of both worlds. In this chapter, we'll explore one method that uses wavelet analysis to enhance detail and two methods that use wavelet analysis to reduce image noise. Wavelet analysis uses functions like the Mexican Hat to split an image into different wavelet scales or levels, each corresponding to a specific band of spatial frequencies. As does convolution, wavelets operate locally on an image and as the Fourier transform does, wavelets allow you to process images in the frequency domain. In this chapter, we shall see how this hybrid between the spatial domain and frequency space produces an powerful image processing tool for astronomy.

Table Of Contents

17.3 Image Processing using the Fourier B.6 Image B.6.1 Image Processing Books General 604 B.6.2 Image Processing Science Applications 605 B.6.3 Image Processing Image Restoration 606 B.6.4 Image Processing and the Fourier Transform 607 B.6.5 Image Processing and Wavelets 607 B.6.6 Image Processing Algorithms 607 B.6.7 Image Processing Software 608 C.7 Image C.9 Multiple Image C.9.2 Multi-Image

The Human Retina

Figure 1.5 The eye is a high-performance imaging system containing a lens, detector array, and an on-board image processing system in the neural network overlying the rods and cones. The eye is so sensitive that under optimal conditions, an observer can see a flash of light consisting of ten photons. Figure 1.5 The eye is a high-performance imaging system containing a lens, detector array, and an on-board image processing system in the neural network overlying the rods and cones. The eye is so sensitive that under optimal conditions, an observer can see a flash of light consisting of ten photons.

Getting the Best Out of Our Camera

Finally there is image processing noise. It may come as a surprise but taking dark frames, bias frames and flat fields and applying them to our image all introduce noise. I am of course not advocating not taking them Just be aware that we must take as much care over these frames as those of the actual image. A flat field

The Panstarrs Cameras

TC3 will also incorporate both wavefront sensors, the deployable Shack-Hartmann apparatus and the continuous curvature sensing optics. TC3 will be used for first light on PS1, and will be populated with the development Lot 1 OTAs which are already in hand. The data from TC3 will provide an excellent data stream for shakedown of the Image Processing Pipeline (IPP). When the PS1 telescope is operating reliably ( June 2006) we will replace TC3 with GPC1.

Is This Really Necessary

Two famous statements made by William Herschel underscore the importance of this lengthy chapter as preparation for observing the Herschel objects. One is that Seeing is in some respect an art, which must be learnt. As described below, there is no doubt that the human eye can be trained to see better in at least four distinct areas involving the viewing of celestial wonders - these being dark adaptation, averted vision, color perception, and visual acuity. And the reason that this is really possible is that the eye works not alone but in conjunction with an amazing image-processing computer - the human brain

Raw vs compressed files

The term raw is not an abbreviation and need not be written in all capital letters it simply means uncooked (unprocessed). Filename extensions for raw images include .CRW and .CR2 (Canon Raw) and .NEF (Nikon Electronic Format). Adobe (the maker of Photoshop) has proposed a standard raw format called .DNG (Digital Negative) and has started distributing a free software tool to convert other raw formats into it.

Point Source Extraction

The PHT Interactive Analysis (PIA) version 7.3 was used with the default settings to reduce the edited raw data to the AAP(Astronomical Analysis Processing) products. At this level of image-processing, the astronomical signals especially at 95 jm are buried under the predominant noise that is caused by drift in the responsivity of the detectors. The responsivity drift was successfully corrected by using the MEDIAN filter routine developed by Kawara et al. (1998) 1 . The drift corrected maps of the four sub-fields are rebinned into 2.3'' pixel at 95jm or 4.6'' pixel at 175jm, and then mosaiced into the 44' x 44' maps of LHEX and LHNW. Finally, the IRAF gauss routine was applied with sigma 6 for smoothing the images.

Observations with the VLA

On 2003 Jan 26.23 UT we detected a radio transient coincident with the optical position of SN2003L. We subsequently initiated an intense radio monitoring campaign at the Very Large Array (VLA) to trace the evolution of the radio emission from the supernova. Data were taken in standard continuum observing mode with a bandwidth of 2 x 50 MHz centered on frequencies 8.5, 15.0 and 22.5 GHz. Flux density measurements were derived using calibrator 3C286 and phase referenced against calibrators J1118+125, J1120+134, and J1103+119. Data were reduced using standard packages within the Astronomical Image Processing System (AIPS). At 8.5 GHz (our most densely sampled light-curve) typical flux uncertainties were 60 Jy for an average integration time of 10 minutes. The results of our radio monitoring campaign of SN2003L are summarized as Fig. 1. These observations demonstrate a broad spectrum, similar to that observed for SN 1998bw.

Smos Concept Demonstration and Product Validation

The maiden flight of AMIRAS took place in June 2006 in the vicinity of Helsinki with the objective to acquire dual-polarisation images of coast lines and islands. An example of the acquired images is presented in Fig. 16. The image processing has focused on Lake Lohja and shows different snapshots (of 1.2 s integration time) of the alias-free field of view as the aircraft enters the lake from the South over a place where there is an island. The range of incidence angles along track varies from 5 to 35 . The coastlines are clearly imaged and geometry is well preserved. The

Apple Ladles on the Sauce

Apple eventually replaced the name 'Macintosh' with the snappier, friendlier 'Mac' and prided itself on the sleek design of its products. A major target area for its goods was the graphics and professional user, both personal and corporate. Programs such as the desktop publishing classic Quark XPress and the graphics programs Photoshop and Illustrator (both by Adobe) were among the cornerstones bolstering the Mac's reputation as being the most desirable graphics and DTP computer. In 1998 Apple produced the eye-catching iMac, an all-in-one device with monitor and computer encapsulated within a streamlined, translucent case (originally a cool blue, but later available in other colors). Apple dispensed with the usual large and unsightly connections (SCSI and ADB) and instead featured two USB ports for peripheral connections. Phenomenal sales of the iMac helped revive the flagging company. at least - is Adobe Photoshop CS2. He doesn't use any 3D programs except Terragen to generate...

Bitmaps TIFFS and JPEGS

Before we leave this introduction to webcams, I would like to add a few words on the subject of image file formats, just in case anyone embarking on webcam work is an image processing novice, too. Most images that are displayed on the web or are sent in e-mails are in the jpeg format and have a file name ending in .jpg. Unlike large, lossless, bitmap (.bmp) and tiff (.tif) files, jpeg files feature lossy image compression. In other words, the size the image takes up on your PC can be reduced considerably at the cost of image quality. Jpeg images are fairly compact, even with zero compression, but to make them smaller they employ a clever mathematical transform that looks at each 8 x 8 pixel block and creates a compact code to economically summarize the data (color and brightness) within each block. With the maximum compression (lowest quality and smallest file size), some 8 x 8 blocks will actually dissolve into one solid 8 x 8 slab with no interior color or brightness variations. We...

Postprocessing Techniques

After you capture a series of long-exposure frames to your computer's hard drive and after you go inside to warm up, it is time to begin the serious task of postprocessing your frames with powerful image processing software. Don't despair. The thing to realize is that the post-processing stage represents half the effort and half the fun This hobby is different from other forms of astrophotography in that it is highly dependent on powerful image processing techniques, and using those techniques to produce a beautiful final image is a large part of the satisfaction. Adobe Photoshop for Windows and Mac Figure 4.10. IC2177, Seagull Nebula. Captured with an SC3 ToUcam by Jim Hommes with an ST f 2.5 scope. 6 x 180 sec H-alpha, 16 x 8 sec IRB, 12 x 12 sec RGB. 4 frame mosaic. K3CDTools, Astroart and Photoshop. Figure 4.10. IC2177, Seagull Nebula. Captured with an SC3 ToUcam by Jim Hommes with an ST f 2.5 scope. 6 x 180 sec H-alpha, 16 x 8 sec IRB, 12 x 12 sec RGB. 4 frame mosaic. K3CDTools,...

Settings for an astrophotography session

Long-Exposure Noise Reduction Your decision. If turned on, this feature will eliminate the hot pixels in your images by taking a dark frame immediately after each picture and automatically subtracting it. This takes time, and as you become more experienced, you'll prefer to take dark frames separately and subtract them during image processing.

Conducting the observations

In addition to your science images, you need dark frames'' and flat frames'' that match the conditions of your science images. The dark frames should be taken at the same exposure and same chip temperature as your science frames. The flat frames can be twilight flats, T-shirt flats, or lightbox flats (whichever is most convenient), and they can be taken either immediately before or after your photometry session. One purpose of flat-fielding is to compensate for the effects of dust donuts'' in the image. Therefore, it is essential that the flat frames be taken through the same V-filter as the science images, and that they be taken before the CCD orientation in the telescope is changed from what it was during the science frames. Otherwise, the dust donuts'' in your science frames won't line up with those on the flat frames. If your image-processing software provides for use of dark flats'' dark frames of the same exposure as your flat frames take those also. If you are an experienced...

Stars from a fixed tripod

The Moon, photographed by holding a Canon Digital Rebel (with 28-mm f 2.8 lens wide open) up to the eyepiece of an 8-inch (20-cm) telescope at x 50. Camera was allowed to autofocus and autoexpose at ISO 200. Picture slightly unsharp-masked in Photoshop. Figure 4.3. The Moon, photographed by holding a Canon Digital Rebel (with 28-mm f 2.8 lens wide open) up to the eyepiece of an 8-inch (20-cm) telescope at x 50. Camera was allowed to autofocus and autoexpose at ISO 200. Picture slightly unsharp-masked in Photoshop. Figure 4.4. Lunar seas and craters. Nikon D70s with 50-mm f 1.8 lens wide open, handheld at the eyepiece of a 5-inch (12.5-cm) telescope at x 39, autofocused and autoexposed. Image was unsharp-masked with Photoshop. Figure 4.4. Lunar seas and craters. Nikon D70s with 50-mm f 1.8 lens wide open, handheld at the eyepiece of a 5-inch (12.5-cm) telescope at x 39, autofocused and autoexposed. Image was unsharp-masked with Photoshop. The picture will benefit...

Imaging and Processing

For processing large raw files, ImagesPlus image processing software is very capable and reliable, able to perform all the necessary steps. First, average the darks and make a master dark of them. Then load the master dark as reference in the calibration setup and calibrate your raw images. If you have vignetting in your optical system, you should also include a flat for calibration. Next step is aligning the calibrated images, easily performed by Image File Operations Align File Translate, Scale, Rotate by marking reference stars. When using Canon raw files, convert them to 16-bit tiff files first, then align and average them in 16 bit. When using 8-bit jpg files, you should use the extended add for combining.

Pluto from Hubble

Two smaller inset pictures at the top are actual images from Hubble (north at top). Each square pixel is more than 160 km (100 miles) across. At this resolution, Hubble discerns roughly 12 major 'regions' where the surface is either bright or dark. The larger images (below) are from a global map constructed through computer image-processing performed on the Hubble data. The tile pattern is an artefact of the image enhancement technique. Opposite hemispheres of Pluto are seen in these two views. Some of the variations across Pluto's surface may be caused by topographic features such as basins, or fresh impact craters. However, most of the surface features unveiled by Hubble, including the prominent northern polar cap, are likely produced by the complex distribution of frosts that migrate across Pluto's surface with its orbital and seasonal cycles and chemical byproducts deposited out of Pluto's nitrogen-methane atmosphere. assembled by computer image-processing software from four...

Reducing and analyzing your observations

Having made a night-long series of images, you're ready for image reduction and data analysis. Image reduction should follow the same procedure as I described in Section 4.3.3 for variable star photometry save your raw images (including darks and flats) on a non-volatile medium do the routine CCD image reduction of flat-fielding and dark-subtraction (and bias subtraction, if you're using scaled dark frames) and do not do any kind of image enhancement algorithm. With your reduced images, you're ready for data analysis. This has three steps finding and following the asteroid, measuring its brightness, and plotting the results. To start, you'll need to find the asteroid in each image so that you can place your photometric measuring aperture directly on it in each image. The standard way to do this is to blink several images in your sequence. The blinking algorithm that comes with most astronomical CCD image-processing software is the digital-age equivalent of the mechanical blink...

T he Role of the c urator

The role of the Curator was various and extremely time consuming. Administratively, it required reminders and regular contact in order to get people online together, and extra time to be available to advise individual participants personally. There was also a great deal of Photoshop work for the curator to do in order to make the images more glass like and compensate for the lack of IT skills in most of the participants.

Vignetting and edgeoffield quality

Vignetting can be corrected by image processing (p. 188), but I prefer to take a more optimistic approach. It's not that the image is small it's that the sensor is big. A DSLR sensor has far more pixels than a typical astronomical CCD, and that means the picture is croppable. You can use a couple of megapixels from the middle of a 10-megapixel sensor and get a very fine image.

Big Gun Number 3 Image Intensifiers

Magnetic Focused Image Intensifier

The third and most important weapon in my city viewing arsenal, after the telescope itself, was the purchase of a modern third generation image intensifier, especially made for astronomy (the remarkable I3 Piece by Collins Electro Optics). The beauty of the Collins device is that you use it just as you would a conventional eyepiece. Image intensifiers require no image processing, monitors or separate controls.

Mercury Map By Mario Frassati

In alphabetical order, the help of the following lunar, planetary, and image processing experts is gratefully acknowledged Cor Berrevoets, Mike Brown, Celestron International, Antonio Cidadao, Jamie Cooper, Mario Frassati, Maurice Gavin, Ed Grafton, David Graham, Paolo Lazzarotti, Isao Miyazaki, NASA JPL, Eric Ng, Gerald North, Donald Parker, Damian Peach, Christophe Pellier, Barry Pemberton (Orion Optics), Maurizio Di Sciullo, Paolo Tanga, Dave Tyler, Unisys Corp., and Jody Wilson (Boston University).

Major manufacturers Canon

Pentax, Sony, Olympus, and other DSLR makers are highly respected but have not achieved a large following among astrophotographers, and I have not tested their products. It is widely rumored that most other manufacturers use Sony CCD sensors similar to Nikon's, although of course the firmware and internal image processing are different. Before buying any camera, you should search the Web and get astrophotographers' opinions of it also make sure its file formats are supported by astrophotography software.

Multipurpose Programs Deepsky 99 v 218 Pcdpsky99

This terrific program offers a planetarium, an observing log, telescope control, some astronomical image processing capabilities, and much more. This demo version includes the i3,000-object database (the Hubble Guide Star Catalog of stars to i5.5 magnitude is available on CD-ROM only), but does not include the massive database of images which is available for download at the Web site.

High Resolution CCD Imaging

Using telescopes as small as 75mm aperture, amateur astronomers are now producing stunning images rivaling those of professional observatories of just a few years ago. The public has been fascinated by the dramatic and colorful highresolution images taken by the Hubble Space Telescope, yet recent amateur astronomical images have been no less inspiring. Over the last few years the art of amateur imaging has made a quantum leap forward with film-format-sized CCDs, professional-quality large-aperture telescopes and sophisticated image-processing techniques all arriving on the scene. Just as important, amateur astronomers have learned how to master them. Figure 8.1. Bubble Nebula, NGC7635. (Ha)(Ha R,G,B) image of 180 30 30 30 minutes total exposures, respectively (3 minute individual exposures for the RGB, 5-minutes for Ha) using a 3nm Ha Custom Scientific Ha filter for the luminance frames and Custom Scientific RGB filters. The 180-minute Ha image was combined 50 50 with the R frame in...

What Is High Resolution

LRGB image of 80 50 50 70 minutes total exposures, respectively (5-minute individual exposures) using a non-IR-blocked luminance image and Custom Scientific RGB filters. Image calibration and color combination using MAXIM DL (RC Console for Sigma Combine and pixel cleanup within Maxim DL), image registration using Registar, Ron Wodaski's gradient removal, AIP for Lucy Richardson deconvolution on the luminance, luminance layering in Photoshop for final color and star shaping processing. Equipment RCOS 20-inch f 8 RC and Finger Lakes IMG6303E CCD camera with all images acquired in 2 x 2 bin mode for an image scale of .92 arcsecond pixel in 2.3 arcsecond seeing and magnitude 4.9 suburban rural skies. Figure 8.2. Galaxy NGC4244. LRGB image of 80 50 50 70 minutes total exposures, respectively (5-minute individual exposures) using a non-IR-blocked luminance image and Custom Scientific RGB filters. Image calibration and color combination using MAXIM DL (RC Console...

How Do I Prepare for High Resolution

L(Ha R)GB image of 150 50 50 70 minutes total exposures, respectively (3-minute individual exposures) using a non-IR-blocked luminance image and Custom Scientific RGB filters. A separate 90-minute Ha image (5-min. individual exposures) was combined 50 50 with the R frame to better highlight the galactic jets. Image calibration and color combination using MAXIM DL (RC Console for sigma combine and pixel cleanup within Maxim DL), image registration using Registar, Ron Wodaski's gradient removal, AIP for Lucy Richardson deconvolution on the luminance, luminance layering in Photoshop for final color and star shaping processing. Equipment RCOS 20-inch f 8 RC and Finger Lakes IMG6303E CCD camera with all images acquired in 2 x 2 bin mode for an image scale of .92 arcsecond pixel in 3 arcsecond seeing and magnitude 4.9 suburban rural skies.

Astrometric reduction software

Your astrometric reduction software can be one of the popular image-processing packages or a more specialized software program. As with photometry, the popular packages (which you may already own) are quite adequate for most projects but the specialized packages have features that may simplify your data analysis or provide improved accuracy. All star charting or planetarium programs contain an internal database of stars. The database entry for each star has its position (RA and Dec), proper motion (maybe), magnitude (usually), and color (sometimes). Most popular programs use the Hubble Space Telescope Guide Star Catalog (GSC) as their faint-star database. This catalog provides accurate positions for all of its stars, and can be used for most amateur astrometric projects. In general, any planetarium or CCD image-processing program that is capable of performing astrometric reductions will automatically select the astrometric stars to use, without bothering you with the details. Examples...

Technical Performance Specifications

Much of ALMA's work will concern extended sources where the extremely high angular resolution needed to meet Requirement 2 is less crucial. The challenge will be to create images with high dynamic range so that faint components can be seen in the presence of bright components. Reducing the number of antennas would reduce the number of different baselines that could be utilized in a single pointing and would distribute the power over the raw map. Some of the lost information could be recovered through image processing, although calibration uncertainties and noise set a fundamental limit to how well the image can be reconstructed.

Spectroscopy with CCDs

Although imaging and photometry have been and continue to be mainstays of astronomical observations, spectroscopy is indeed the premier method by which we can learn the physics that occurs within or near the object under study. Photographic plates obtained the first astronomical spectra of bright stars in the late nineteenth century, while the early twentieth century saw the hand-in-hand development of astronomical spectroscopy and atomic physics. Astronomical spectroscopy with photographic plates, or with some method of image enhancement placed in front of a photographic plate, has led to numerous discoveries and formed the basis for modern astrophysics. Astronomical spectra have also had a profound influence on the development of the fields of quantum mechanics and the physics of extreme environments.1 The low quantum efficiency and nonlinear response of photographic plates placed the ultimate limiting factors on their use.

Using a Charged Coupled Device CCD

The magazine Sky and Telescope maintains a Web site specifically for CCD topics. You can find it at http www.skypub.com iwaging ccd ccd.shtml. At the Web site, you will discover articles such as Starting out Right in CCD Imaging, Optimizing a CCD Imaging System, Image Processing Basics, and a few others. This is really a nice place to get a basic start in CCD imaging.

Other Things to Image

In the above sections I have discussed imaging nebulae (dark, emission and reflection), clusters (open and globular) and galaxies of all types. The objects chosen have been suggested as good first targets for the beginner. Is there anything else If you take a look at the Chapter 11 images, you'll see there is something else, but it takes a lot of image processing practice to make these objects look as good as they do in that Chapter. These objects are single (or double) bright stars, with a nice background star field.

Analyzing reducing and reporting your results

Some observers are experimenting with frame grabbers and digital image-processing methods to pre-screen the video, (hopefully) simplify the detection process, and (again hopefully) improve the odds of detecting flashes that are embedded in the video. If these developments are successful, you'll see reports on the ALPO website. If you are experienced with this technology, you should definitely consider bringing it to bear on your video data.

The God of the Heavens a Triumph of Persistence

While Voyager 2 logged plenty of new moons during the flyby, it found very little of visual interest in Uranus itself. At visible wavelengths, the planet was a bland uniform blue and green with no sign of the vibrant cloud bands of Jupiter or even the more subtle ones of Saturn. Some years later, the Hubble Space Telescope would image Uranus at wavelengths that were not available to Voyager and image processing tools that could only have been dreamed of in 1986. Uranus grudgingly began to reveal signs of circulation in its atmosphere. Also in 1986, Uranus' south pole was pointing almost directly at the Sun. In the early part of this decade, the Sun was moving much more towards the equator in the Uranian sky. This probably causes more diurnal variations in weather in the atmosphere and thus Uranus appears to be a much more vibrant place than it was when Voyager flew by it 20 years ago. Voyager discovered that Uranus is a very different kind of world than are Jupiter and Saturn. Uranus...

Must we make corrections

The galaxy M51, without guiding corrections. Enlarged central part of a much larger picture. Stack of three 3-minute exposures, minus dark frames, with 8-inch (20-cm) telescope at f 5.6 and Canon Digital Rebel (300D) camera at ISO 400, processed with ImagesPlus, Photoshop, and Neat Image.

Observing Projects 11B Uranus and Neptune in the Camera

The optimized astronomical CCD is far better for this application because of its sensitivity and its speed. Make sure that chip is properly chilled and take progressively longer test images. Experiment with the settings to make sure you can process the noise out of your images and eventually you will begin to reach the level of the faint moons. Also always remember never to give up on a bad image because as your image processing skills at the computer get better, you will be able to pull good signal out of even the noisiest images. And when you're imaging down to magnitude +14, you're going to get a lot of noise.

Society of Amateur Radio Astronomers SARA

The astronomer may wish to examine the data in detail, displaying it in different ways, experimenting with image processing techniques, probing for the secrets it contains. The Flexible Image Transport System (FITS), developed by astronomers to encode definitions of image data and the data themselves, is a platform-independent system now widely used for interchanging data between observatories that has also become widely used outside astronomy. The main astronomical data reduction systems are NOAO's Image Reduction and Analysis Facility (IRAF) and ESO's Munich Image Data Analysis System (MIDAS) in the optical region, and NRAO's Astronomical Image Processing System (AIPS, and its successor, AIPS++) in the radio region. These can be seen as software component frameworks, with a structure that allows new components to be added easily and provides most of the basic services (for example data file access, user interaction) that the new component needs. Data acquisition systems can be...

Layer Oriented Wfs Lowfs

The issue of different horizontal binning factors for the two CCDs was addressed by a clock pattern that bins four pixels on one CCD, but only two pixels on the other by omitting clock transitions on the latter. As the standard FIERA software expects an equal number of pixels to be read from all CCDs, dummy pixels are read from the CCD with the higher binning factor. They are ignored by the subsequent image processing routines. A similar method is applied for the vertical binning. While the first CCD is subject to four line shifts two of them are skipped on the second device.

Surface distribution 2D statistics

The distribution of objects on the celestial sphere, or on an imaged patch of this sphere, has ever been a major preoccupation of astronomers. Avoiding here the science of image processing, the province of thousands of books and papers, we consider some of the common statistical approaches used to quantify sky distributions in order to permit contact with theory. Before we turn to the adopted statistical weaponry of galaxy distribution, we discuss some general statistics applicable to the spherical surface.

Photometry Capable Computer Programs

Both of these methods are beyond the scope of this book but there are several books available to assist you should you begin CCD or PEP observations. A few that I would recommend are The Handbook of Astronomical Image Processing, by Richard Berry and James Burnell Photoelectric Photometry of Variable Stars, by Douglas Hall and Russell Genet and Astronomical Photometry by Arne Henden and Ronald Kaitchuck, all published by Willmann-Bell. Also, Arne tells me that he has a new CCD photometry book coming out after this one, so keep an eye open for it.

Image Reduction Calibration

The first step in processing your exposures should be the dark frame subtraction and flat-field correction. Some programs, like CCDSoft, call this process image reduction, whereas other programs, like Maxim DL, call this image calibration. Most image processing programs have a routine to perform this efficiently on all of your images. Make sure that the dark frames match the temperature, the exposure time, and the bin mode of your light exposures. Also, confirm that your flat fields match the optical system of your light exposures. See the section on Combining Images for suggestions on dark frame and flat-field combining.

Histograms brightness and contrast 1341 Histograms

A common task is to equalize the histogram, i.e., spread out the pixel values so that more of the range is used. This can be done with the Levels adjustment in Photoshop (which looks like Figure 13.4) or the corresponding adjustment in MaxDSLR or other software. Almost all image processing software lets you adjust curves. For one example, see p. 158, and for a whole gallery of curve adjustments with their effects, see Astrophotography for the Amateur (1999), pp. 226-228.

United Kingdom Schmidt Telescope UKST Large

United States Geological Survey (USGS) Sole science agency for the US Department of the Interior. Its Flagstaff Field Center was established in Arizona in 1963, originally for lunar studies and training astronauts for the apollo programme in geology. Since then, Flagstaff's activities have expanded to include the study of the origin and evolution of the terrestrial planets and the major satellites of the Solar System, the development of techniques of remote sensing and image processing to aid in the interpretation of planetary surfaces, and to produce topographic and geological maps of planetary bodies.

Processing the Combined File Dataset

There are many good tutorials and some books available on processing your astronomical images. I have Jerry Lodriguss' Photoshop for Astrophotogra-phers and I also check out Rob Gendler's http www.robgendlerastropics.com processing tips, as well as Steve Cannistra's http www.starrywonders.com on a regular basis. Ron Wodaski http www.newastro.com wodaski also has some very nice image processing tutorials on his website. However, when all is said and done, there is no substitute for getting the colour-converted raw image into an image-processing package and simply having a go at some digital image processing. There are probably more than 3 Golden Rules, but I find these three must be adhered to at all times. Golden Rule number 1 Do not clip the light point. Golden Rule number 2 Do not clip the dark point. Golden Rule number 3 I think the only way to see how to use the available tools is by practical example. So you will be able to download some raw data and try these things out for...

Now the Hard Work Begins

I usually open the patrol images, up to 50 at a time, and then selectively open masters one by one. This allows the image settings to be changed to display the inner and outer parts of the galaxy image alternately. As well as looking for possible supernovae, I compare the new image just taken with the older master image. If it is of higher quality, I replace it. The master image stored on the hard drive is therefore the best image that I have ever taken of that particular galaxy. It is essential to use your own master images. They match your telescope setup and the color response of your camera. This saves a lot of time and helps you to dismiss unlikely candidates quicker and recognize potential candidates more easily. By all means, check your images against the Palomar Sky Survey, particularly the second-generation plates. Indeed, the Central Bureau (CBAT) will require you to have done this before submitting your report on a suspect. This is to support your...

Image Sharpening and Blurring

Bright areas of an image have enough signal to benefit from sharpening. Dark areas of an image have weak signal, giving rise to a grainy appearance that could benefit from blurring. Most astronomical image programs have the filters to both sharpen images and blur images. The disadvantage of these routines is that they usually apply to the entire image. Photoshop has the ability to select a region of the image to apply the filter selectively. The easiest sharpening tool is unsharp masking. Typically, choose an amount between 50 and 100 , a radius of 3-5 pixels, and a threshold of 0 if you have a good image, but a higher threshold if your image is noisy. A more precise sharpening tool is smart sharpen, that is only available on more recent versions of Photoshop. As with unsharp masking, choose an amount of 50-100 and a radius of about 5 pixels. If your sharpening effect is too harsh, fade the application of sharpening to less than 100 . If your sharpening was on an RGB image, fade the...

Removing grain and lowlevel noise

A better approach is to try to distinguish intelligently between grain and signal. One piece of software that does an impressive job of this is Neat Image (www.neatimage.com), available both as a standalone package and as a Photoshop plug-in. As Figure 14.9 shows, Neat Image can almost work magic. The noise reduction filter in Photoshop CS2 is much less potent.

Dealing out Gradients

Within Photoshop, you can use the image itself to create a model of the sky gradient if the celestial target is either an open cluster or a well-defined nebula or galaxy that occupies less then a quarter of the image. Flatten the image (if not already flattened) and then duplicate the background layer. Choose the copy, and select color range - shadows. Select inverse, and then cut the selection. Apply a large Gaussian blur of about 50 or more pixels. Change the blend mode to difference, and reduce the opacity to about 80 . Your sky gradient should be almost invisible. This technique fails with larger faint nebula or galaxies because the faint detail can be erased and gradients superimposed directly on the target are not eliminated. Other methods in Photoshop work for larger objects, using the gradient tool. This technique begins with a new blank layer that is filled with a gradient from sampled foreground in the brightest corner of your image to sampled background in the opposite...

Some basics of image displays and color images

Terms are fully explored in Gonzalez & Woods (1993) as well as in almost any text introducing image processing techniques. To avoid such poor scaling and loss of visual information, two alternatives generally exist one uses a linear scaling but within a specific data window and one uses a different type of scaling altogether. The first option is accomplished by having the software again perform a linear scaling but this time using its 200 output display levels to scale image data values only within the data window of say 0 to 2000. Different scaling options allow for nonlinear modes such as log scaling, exponential scaling, histogram equalization, and many others. These are easily explored in any of the numerous image processing software packages used today. Further information on general image processing techniques can be found in Gonzalez & Woods (1993), while additional details on image displays can be found in Hanisch (1992). User manuals for astronomical image processing...

The extreme brightness range of nebulae 1451 Simple techniques

Levels or curve shape helps bring out the faint regions without turning the bright regions into featureless white. A good tactic in Photoshop is to adjust the Levels slider several times in small, careful steps. A very powerful way to combine different exposures is to use layer masking in Photoshop. This technique has been perfected and popularized by Jerry Lodriguss (www.astropix.com). Figure 14.10 shows what it accomplishes. The key idea is that the shorter exposure replaces the longer one in the parts of the latter that are overexposed. I'm going to give quick instructions for this technique here, but if you are not very familiar with Photoshop, you may also need to consult additional documentation. (2) Align them, preferably using astronomical software (see p. 154), but do not stack them. Instead, save the aligned images in a form that you can open in Photoshop. (4) Open all three in Photoshop. The image you are going to edit contains a copy of the longer exposure. Figure 14.11....

CCDs for college teaching

Complete thermoelectrically cooled CCD cameras packaged into small units ready for attaching to modest-sized telescopes have flooded onto the market and opened up a great opportunity for amateur astronomers and for teaching uses at schools, colleges, and universities. If you are reading this book it is likely that you have access to a CCD camera. A wide variety of cameras are available with small CCDs of only 192 x 165 pixels such as the TC211, up to those with 2,048 x 2,048 pixels like the Kodak KAF4200. Some companies sell only the camera heads and electronics while others provide PC-based image-processing software ready to support popular cameras. A few companies provide complete turn-key packages containing camera, computer, and software ready to control your small telescope. One of the best resources is to look at the ads placed in magazines such as Sky & Telescope and then go to the web sites of the companies involved.

Quick Process of a Single Frame of the Pleiades

What we are going to do with this image is to split it up into separate Luminance (L), and Red (R), Green (G), and Blue (B) files. We will then do a little image processing on the L file only before recombining all four files back into a colour image. PhotoShop Processing of the Pleiades Data and Use of Noel Carboni's Actions Before we begin there are two things about PhotoShop and astronomical imaging processing. One, PhotoShop is plain scary, it looks big and intimidating and it is big and intimidating. Some people can have a day job based on the fact that they can run PhotoShop - it's that big. The second thing we need to know is the shape of the Magic Curve mentioned in the Golden Rules. We shall use a nonlinear stretching routine in PhotoShop called curves to pull out the faint stuff in the same way that we used the DDP FFT function above in Maxim DL. However, you need to get the shape of the curve you are going to use correct, or you will blow up the stars as well as bring out...

Refractor or Reflector or Perhaps Both

Split the light up into its constituent colours as it passed through the optical system, and finally the different colours would be focused in slightly different positions at the eyepiece end. There are filters you can use to cut down these unwanted effects, and these are usually referred to as fringe-killers. These filters cut down the blue and infrared wavelengths passing through your refractor minimising the blue halos, and the bloated (oversize) stars caused mainly by the near infrared radiation your CCD camera will be sensitive to. Since your CCD camera is invariably based on Silicon technology, it will detect radiation up to near 1 micron (10-6m) in wavelength. Very deep red extends to around 0.695 microns, so the CCD is sensitive well beyond the eye's visible wavelength limit and it extends your detection limits to the near infrared. The filter may sound like a good way of turning a cheap refractor into an effective apochromat for imaging purposes, but of course there is a...

Narrowband Imaging and Light Pollution Filters

Computational Considerations -Data Acquisition and Image Processing Many people, myself included, start off by taking their laptop out to the observatory and using that to acquire the CCD data and to look after the scope driving and autoguiding. The software for downloading the CCD data, and autoguiding can be the native camera software, or it can be specialist software specifically written for carrying out the tasks, including image processing. I have used AstroArt http www.msb-astroart.com to great effect (AstroArt also has a great photometry package amongst many other goodies), but I currently use Maxim DL http www.cyanogen.com for all data acquisition, autoguiding, colour conversion and stacking. Returning to hardware considerations, any current model laptop is going to be good enough to carry out these tasks provided it has a fast USB 2.0 interface available for downloading the data from the CCD camera. Any reasonable size hard drive will also be more than adequate for storing a...

Software for the Task

The Sky has always been the planetarium package that advanced amateur astronomers have regarded as the gold standard. It has never been an inexpensive package, although you can now buy it in cut down Serious Astronomer and Student editions. The Sky is probably the only package here that can justify the term professional as it is used in thousands of advanced amateur and professional observatories to control telescopes that are involved in real science. This is a planetarium package that leaves nothing scientific out new discoveries are seamlessly uploaded from the Web. All the scientific data you could ever want is here, if your aim is to explore the night sky. Unlike some competing packages, you will not get dozens of animated tours and you will not feel like you are in a spaceship. The current version 6 is much prettier than version 5 and The Sky 6 display combines beauty and science perfectly. This is the package that the serious amateur astronomer will want to control his or her...

C1 False color and pseudocolor images

If we combine three optical images in a manner akin to how our eyes would see it, e.g., with similar intensity ratios for red, green, and blue light, the image is called a true color image. As usual, the best way to learn all about color imagery is to experiment yourself. Programs such as The Gimp, XV, Photoshop, and others can be used for this purpose. An excellent account of how to produce color astronomical images including all the factors and intricacies involved, as well as examples, is provided in Rector et al. (2005).

The camera as your logbook

Digital cameras record a remarkable amount of information about each exposure. This is often called EXIF data (EXIF is actually one of several formats for recording it), and Windows itself, as well as many software packages, can read the EXIF data in JPEG files. Photoshop and other utilities can read the same kind of data in raw files. From this book's Web site (www.dslrbook.com) you can get a utility, EXIFLOG, that reads a set of digital image files and generates a list of exposures.

A fender crisis averted

In 1971, John Lowry launched a new company called Image Transform in North Hollywood, California. Lowry had worked for years in the film and TV industry and had developed the means of dramatically improving the image quality of video tape-to-film transfers. He received six image processing patents at the time for video noise reduction and other related developments. He was given some video footage from Apollo 15 to clean up, and the results impressed even Lowry himself, improving the video signal-to-noise ratio by 3 to 6 db. He felt he could make a contribution towards improving the video images for future Apollo missions and in February 1972, two months before the launch of Apollo 16, Lowry met with Col. James McDivitt at the Manned Spacecraft Center in Houston. Lowry brought with him three short clips from Apollo 15 to show McDivitt, of both before and after the image transfer process. McDivitt was impressed and Lowry's company

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