Many of us look at the night sky with wonder and amazement at its sheer immensity, an immensity that only grows as we use telescopic instruments to gather more light than we can see with the naked eye. A step beyond simple observing by peering through an eyepiece is attaching a camera to a telescope and making time exposures to gather yet more and more light. This is how deep-sky images are created.

The process generally is much more complex than that. There are several things to be worked out, such as whether to use a reflecting or refracting telescope, type of camera and lens, and details such as aligning the camera’s imaging chip to be as close to perfectly flat relative to the incoming light as possible. When capturing images, the earth’s rotation requires the telescope to be guided during an exposure to remain fixed on the target. Many sub-exposures of several minutes each, overall taking hours to complete, may be required. An object larger than the camera’s field of view requires several sets of images to be taken of parts of the whole, and then joined as a mosaic. The raw data from the sub-exposures are captured onto a computer hard drive, and then combined together additively with specialized software to produce a sufficiently strong and detailed image. For a mosaic, the several parts must be joined using other software. Finally, post-processing with image editing software such as Photoshop, augmented with astronomical image processing add-ons, is used for such finishing touches as adjusting the colors or removing aberrations, to arrive at the end goal of making a “pretty picture” as author Greg Parker describes it. He presents many pretty pictures he made in his book.

Clearly a labor of love, Parker describes how he came to be interested in astronomical imaging. We learn about the hobby through his descriptions of equipment and software he found and employed over the years, and the mistakes he made as he developed his expertise. The novice reader should not be put off by the technical descriptions in the introduction--all is explained in detail later on. It helps, of course, if the reader has some familiarity with cameras, telescopes, and how to install and use relevant computer applications when beginning the book. Parker provides many references: places to get general information about celestial objects; how to operate a telescope, cameras, and lenses; how to use Photoshop; and so on. He describes hardware and software he personally uses, but one can apply what he says to researching alternatives. Also of interest is his description of how to obtain professional image data from the Internet to produce one’s own pictures. The writing is very clear, offering many tips and techniques.

The impression I got from the book is that deep-sky imaging is a serious hobby, one that will take a lot of time to get good results. Much of that time will be spent in the middle of the night. Someone who approaches this hobby casually likely will be disappointed with the outcome. Parker’s dedication shows in the beautiful images he displays in chapter 13. The images are that much more impressive given that he used consumer-level equipment to make them, as opposed to very high-end, professional, and large diameter observatory equipment. This book will be a valuable reference to anyone wishing to get started in this fascinating hobby.

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