The purpose of this book is to serve as a practical guide to astrophotography with digital single lens reflex (DSLR) cameras. It explains how digital cameras work and everything you need to know about how to take astrophotos with them. It also tells you how to digitally process the images after you have shot them, with step-by-step directions that will produce beautiful results.

The popularity of DSLR cameras for regular photography has exploded. Digital cameras have replaced film cameras as the prime driving force in both marketing and technological innovation by camera manufacturers. Because of this, the overwhelming majority of research and development investments and effort is now in digital cameras. This has paid off with advances in every new camera generation offering more powerful features and lower prices. Of particular interest to astrophotographers is the increasing improvements in the low-noise capabilities of these cameras.

The latest generations of DSLR cameras with extremely low-noise properties make them ideal for astrophotography. These cameras are primarily designed for normal daytime photography, but they are capable of taking remarkably beautiful images of celestial objects.

Because their price and features are so attractive, and because these cameras are so versatile, many amateur astronomers have been adopting them for astrophotography. This book is aimed at helping them in using DSLR cameras in capturing the beauty and wonder of the night sky. All of the how-to information presented in this book is based on real-world experience with current equipment. It is also written with technical explanations that do not underestimate the intelligence of its readers.

Background

I first started taking pictures in the early 1970's when I bought a camera to shoot through my telescope. I promptly fell in love with photography, both in the daytime and at night.

Sports was also one of my interests. When I found out that I had a talent for follow-focus with manual-focus telephoto lenses, and that there were newspapers that would actually pay me to take photos at sporting events, I had a way to make a living with what was originally just a hobby. Now I've been a professional sports photographer and astrophotographer for more than 30 years.

I started shooting sports with DSLR cameras in the mid 1990's, and have always tried to do astrophotography with them. The results were disappointing for many years because the noise generated in long exposures made them difficult, if not impossible, to use for really high quality long-exposure astrophotography.

In 2004 a new generation of very low-noise DSLR cameras, including the Canon EOS 20D and Nikon D70, were introduced. 2005 saw the introduction of the remarkable Canon EOS 20Da, a DSLR camera specifically made for long-exposure astrophotography. In that year the low-noise, very modestly priced Nikon D50 was also introduced.

I purchased a Canon 20Da shortly after they were introduced, and began the writing of this book. The material contained here comes from personal hands-on experience in using Nikon and Canon DSLR cameras for astrophotography. As I worked with these cameras and learned how to use them for astrophotography, I realized that every question and problem that I had, other astrophotographers would also have. The answers to these questions and solutions to these problems collected in a book will hopefully be a resource for other photographers.

Organization and Contents

A Gallery of Digital Astrophotography presents my best astrophoto images taken with DSLR cameras. Technical data, such as exposure time, ISO, and telescope / camera lens for the photo is also given along with a brief description of the image processing details.

Chapter 1 discusses the different types of digital cameras that are available such as digital snapshot cameras, astronomical CCD (Charge Coupled Device) cameras, webcams and DSLR cameras. The benefits of film vs CCD vs DSLR cameras for astrophotography are covered, as well as DSLR camera attributes and features. Specific cameras are recommended for astrophotography.

Chapter 2 covers cameras, tripods, lenses, telescope, mounts, and accessories you will need, as well as image processing software and hardware. Specific recommendations for combinations of equipment are made for different budgetary ranges.

Chapter 3 gets into the specifics of how digital cameras work to convert photons of light to digital information that we can work with on our computers. Signals and noise in DSLR cameras is discussed as well as ways to improve the signal-to-noise ratio in images.

Chapter 4 talks about beginner, intermediate and advanced astrophotography techniques. The beginner section covers photography of the Sun and Moon, scenics, star trails and constellations and the Milky Way. Intermediate astrophotography discusses afocal, wide-angle, telephoto, piggy-back, and eyepiece projection astrophotography. The section on advanced astrophotography covers, in depth, long-exposure deep-sky imaging. Filtered shots and high-resolution planetary images are also discussed.

Chapter 5 gives detailed, step-by-step, instructions for image processing both JPEG and raw images. Basic correction of color and brightness, as well as techniques for enhancing images, sharpening and reducing noise are covered. In the advanced image processing section, you will learn how to correctly calibrate raw images with support frames such as dark frames, stack multiple shorter exposures to equal longer ones, and apply non-linear processing through techniques such as digital development. Special advanced techniques such as high-pass filtering, layer masks, and channel substitution are also covered.

Chapter 6 covers the different types of file formats, and methods of storing files for permanent archival storage. Resolution and file sizes, color management, and outputting to a web page or printer is also discussed.

The appendix contains detailed references and resources for each chapter as well as information on formulas for astrophotography and equipment tests. Detailed equipment checklists, and setup instructions for cameras are included.

More than 100 minutes of video tutorials for image processing of both JPEG and Raw images are included in the appendix.

A powerful built-in search engine provides automatic links to the pages containing the search terms.

A glossary gives definitions of all of the technical terms used in the book.

Original Raw image files for M33 are also included on the CD-ROM so you can follow step-by-step with the Advanced Processing examples with the actual files used in the examples. The dark, flat-field, and bias support frames for the raw light frames are also included for calibration. The JPEG original of Orion used in the basic JPEG image processing example is also included.

The Book's Format

This book on CD-Rom is presented in web page format that can be viewed in any web browser such as Internet Explorer, Firefox, Netscape, or Safari.

It is formatted so that pages can be printed out directly from your browser.

A unique feature and advantage of this book compared to a traditional paper book is its "mouse-over" image comparisons. When a technique has a comparison between before-and-after images to illustrate it, instead of the images being presented side by side with smaller images due to the limited page width, the comparison images are presented at full-page width combined with the mouse-over feature. All the reader has to do is hold the mouse cursor over the image to see the before and after images. In this way the images can be instantly compared more conveniently and at a larger size than would have been possible in a traditional paper book. Note that you must have Javascript enabled in your browser to be able to use the mouse-over image comparisons.

Links

One of the features you will find in this book is live links to web pages on the internet. For example, if I mention a particular camera or accessory, I may link to a location on the internet where you can buy it or get more information about it.

I think this is a very useful feature that is much easier to use than typing in a full URL from a traditional printed book. However, things change fast on the internet and frequently links will be broken for reasons such as the original authors changing their location, or re-organizing their sites.

It can be irritating when you click on a link and it doesn't work. So that presented me with a dilemma. Do I use live links in the book with their ease and convenience, but at the risk of broken links that will occur over time? Or do I leave them out altogether so the book doesn't appear out-dated?

I decided to leave the live links in, even at the risk of some of them going bad, which some undoubtedly will, because they are so relevant and convenient. Even if a link is broken, you will usually be taken to the web site's home page where you can do a simple search for the item and usually find its new location. And many of the links will remain good for long periods of time.

Note that you must be connected to the internet when you click on a link in the book for it to work.

A Note about Internet Explorer and Active Content

When trying to view the pages of this book in some versions of Microsoft's Internet Explorer browser, a warning message may be displayed that looks like this:

You can click on this information bar and select "Allow blocked content" if you want to see the mouse over illustrations and video tutorials or, you can use a browser like Firefox that does not have these kinds of security problems.

The "active content" that Internet Explorer is blocking are tiny snippets of javascript that allow the images to change on mouse-overs, and other javascript that allows the videos to play. This CD-ROM has been thoroughly scanned for viruses and nothing on it presents any threat to your computer. If you trust the author and publisher, please allow this blocked content in Internet Explorer, or switch to another browser. If not, please return the CD for a full refund.

Acknowledgements

I would like to thank everyone who has helped me in the preparation of this book, and especially Chuck Vaughn, Wei-Hao Wang, Al Kelly, Terry Lovejoy, Don Westergren, Mike Unsold, Jim Solomon, Scott Manning, Jim Sweeney, Alan Daroff, Lane Davis and John Martinez.