The Art of Astrophotography

Book Preface

The first point to address is why the title ‘The Art of Astrophotography’ was chosen for this book. As one finds when setting out to produce beautiful astronomical images, as much, or even more, time is spent processing the data as acquiring the raw data. There are many image processing tools available, some of which will be applicable to a particular image, and the appropriate ones need to be chosen and applied to give the desired result. Different images will require a different sequence of processes and rarely will these be the same, so there are no rigid rules as to how to go about it. There is thus some ‘art’ required to choose the appropriate tools to produce a particular image. But then, having produced an image, artistry is often required to make it aesthetically pleasing, so this is perhaps a further and more common use of the word ‘art’ as applied to astrophotography. Two examples of, hopefully, applying artistry in the production of an image are seen in the ‘Star Trails’ and ‘Composite Meteor Trails’ images in Chapters 1 and 17 respectively.

Software is extensively used not just for image acquisition but for processing the captured images. Happily, many of the required software tools are free, such as Deep Sky Stacker (DSS) and Registax, but specialist programs that are used to process astronomical data such as Pixinsight need to be purchased. One often finds that, having done the major part of the image processing in a specialist program, Adobe Photoshop is used to carry out the final editing of the image. The important point about Photoshop is that it can handle 16- bit data which less expensive programs such as Photoshop Elements cannot do. At the time of writing, the free program GIMP can also only handle 8- bit data, but it is said that the next version will be able to do so and thus this may then become an alternative to the use of Photoshop.

In this book all the image processing is handled in Photoshop. Adobe no longer sell the CS6 version (or any previous versions) of the program and it is leased on a month to month basis, so, at least, there is no large upfront cost. All of the capabilities required for the image processing techniques used in this book are found in the versions from CS2 onwards (I use an ‘academic’ version of CS4). It is sometimes possible to buy new copies of these older versions by searching on the Internet and, should you not have a copy of Photoshop, I would encourage you to search for ‘Adobe Photoshop CS2’ to see what might be available.

The structure of the book is very simple. Relatively short chapters are used to illustrate virtually all aspects of astrophotography and are used essentially as ‘worked examples’, first describing the hardware that would be needed to capture a particular image and then describing, step by step, how the image is processed to produce the final result. As the chapters progress, the equipment required will become more complex, but they start with two chapters whose images require only the use of a DSLR (digital single lens reflex camera) and a tripod.

A few chapters introduce techniques that can aid all aspects of astroimaging, such as Chapter 10, which describes how DSLRs can be cooled to enhance their performance in summer, and Chapter 12, which shows how filters can be used to combat light pollution.

Gradually, all of the processing steps needed to create images are covered – in detail when first applied in the early chapters, and then with a summary of their use in later chapters. So even if one only wishes to use, for example, a telescope, equatorial mount and cooled CCD (charge- coupled device) camera, the earlier chapters should at least be read lightly.

The book’s chapters are supplemented with a set of appendices to cover in more depth aspects of astroimaging that are briefly summarised within some of the chapters. Examples of appendices where introductory chapters are included in the main text are Appendices A and D relating to telescopes and autoguiding. A further appendix, Appendix B, discusses in some depth the mounts, alt/ az or equatorial, that are such an important part of an imaging system.

The world’s top astrophotgraphers tend to concentrate on one aspect of the hobby – and do it supremely well. Damian Peach’s planetary images come to mind. Over the past few years I have been writing books and articles – most recently a series entitled ‘Imaging for Beginners’ for the UK magazine Astronomy Now – which have had to cover all aspects of astroimaging, so in one sense I am a ‘jack of all trades’ but master of none. (But, having said that, one of my lunar images has been awarded a trophy and a variety of others have been used in books and magazines to illustrate articles other than those of my own.)