We are indebted to our contributors, Drs. Baraff, Chervenak, Childers, and Jones. In addition to contributing Hacks of their own, they also reviewed everything we wrote and made numerous helpful additions, suggestions, and corrections. Thanks to their help, this is a much better book than it would otherwise have been.

We also want to thank Mark Brokering at O'Reilly, who got the ball rolling and kept us on track. And without Brian Jepson, our editor, this book would never have seen the light of day (or the dark of night). Thanks, guys!

Thanks are also due to Al Nagler, the founder of Tele Vue Optics, Inc., who came to our rescue on very short notice when we desperately needed an image of a top-quality refractor for the front cover. The cover photograph is a Tele Vue-NP101 101mm f/5.4 apochromatic refractor on an ash-wood Tele Vue Gibraltar mount, a world-class instrument that any astronomer would be proud to own. For more information, visit the Tele Vue web site at


    Astronomy Hacks happened almost by accident. Our editor emailed us one day to say that O'Reilly was thinking about doing an astronomy book and to ask if we knew any amateur astronomers who might be interested in writing it. We sent a one-sentence reply, "Other than us, you mean?"

    Of course, once O'Reilly realized that we were amateur astronomers, there never was much doubt about who would write the book. Robert was drooling at the thought of it. Barbara is too refined to drool, but she, too, was excited about the opportunity to write about our shared hobby. We had other high-priority books in progress, but this opportunity was too good to miss. So we dropped everything to write Astronomy Hacks. Writing about computers, our usual day job, is fun. We like computers, and we like writing about them. But we love astronomy.

    There is something special about being out under the night sky. We look up and see the stars and constellations, just as our many-times-great grandparents did hundreds and thousands of years ago. The stars provide a link across the generations, from remotest antiquity down to the present day. They establish an unchanging framework that places us in context within the universe.

    We look at the Great Orion Nebula, for example, and realize that the light we see tonight began its journey about 1,550 years ago, when the Roman Empire was in its final days. Or we view the Andromeda Galaxy and realize that the photons striking our eyes left Andromeda about 2.9 million years ago, when early proto-humans were just coming down from the trees. And, as we look at the dim smudge of Andromeda and remember that that smudge is actually the light from nearly a thousand billion Suns, we wonder if someone there is looking back at us, wondering the same thing.

    So, we jumped at the opportunity to write Astronomy Hacks. We had two goals in writing this book. First, of course, we wanted to convey our passion about astronomy to those many people who have some interest in the stars but have not yet begun their personal journeys of exploration and to encourage them along that road. But we also wanted to "pay forward." Over the years, many experienced amateur astronomers helped us learn the ropes. There's no way we can ever pay them back, but we can pay forward by helping others to learn and enjoy the hobby.

      Why Astronomy Hacks?

      The term hacking has a bad reputation in the press. They use it to refer to people who break into systems or wreak havoc with computers as their weapons. Among people who write code, though, the term hack refers to a "quick-and-dirty" solution to a problem, or a clever way to get something done. And the term hacker is taken very much as a compliment, referring to someone as being creative, having the technical chops to get things done. The Hacks series is an attempt to reclaim the word, document the good ways people are hacking, and pass the hacker ethic of creative participation on to the uninitiated. Seeing how others approach systems and problems is often the quickest way to learn about a technology.

      When we were growing up in the 1960s, kids didn't sit around playing video games, listening to CDs, or watching DVDs. We did things. We ground our own telescope mirrors with blanks and grit purchased from Edmund Scientific (which is now, alas, a very pale shadow of what it once was), and built our scopes from Sonotube and pipe fittings. We built ham radio rigs from mostly scrounged components, and assembled rockets from salvaged conduit and army-surplus gyros (and concocted our own fuels). We tapped our girlfriends' telephone lines, learned how to pick locks, and built darkrooms in the basement. We forged drivers licenses, tore down and rebuilt car engines, repaired our relatives' televisions and appliances, constructed silencers for our .22 squirrel rifles, and made general nuisances of ourselves. In other words, we spent most of our free time hacking, although the term had not yet been invented.

      Nowadays, most of what we did would quickly land us in a federal penitentiary. Back then, adults smiled, shook their heads, and told themselves that "boys will be boys" (even though some of us were girls). Most of those hacking opportunities are gone now, more's the pity. Hams buy most of their gear now rather than building it, and "rocket kits" and "chemistry sets" have been gutted to the point of worthlessness by companies fearful of litigation. Cops no longer have a sense of humor about teenagers' antics, and tearing down your car's engine will probably earn you a visit from EPA agents in black helicopters. What's a would-be hacker to do?

      Well, there's still astronomy, which is one of the few remaining technical hobbies where hacking is not the exception, but the norm. Hacking is a time-honored practice among amateur astronomers, although most would not call it by that name. Many amateur astronomers still build their own telescopestwo of our contributors didbut even if that's a bit beyond your abilities, there are many other opportunities to hack.

      But hacking doesn't just mean doing things; it means having a deep understanding of those things. At one level, it's possible to enjoy amateur astronomy without understanding any of the technical details. At its simplest, amateur astronomy requires nothing more than the night sky and your Mark I eyeball. Ultimately, though, you'll probably want to see more than is visible with your naked eye and to know more about what you're seeing.

      That's where Astronomy Hacks comes in. Over the years, we've helped a lot of newbies over the hump, so we know the issues that beginning astronomers (and even more experienced ones) trip over. Astronomy Hacks is a collection of hard-won knowledgeeverything from advice on choosing, using, and maintaining equipment to observing tips and tricks to short essays that explain the essential concepts you need to understand to more fully enjoy the hobby. Astronomy Hacks will help you get up to speed quickly, spend your money wisely, and bypass many of the frustrations beginners usually encounter. We tried to make this book the next best thing to having an experienced astronomer looking over your shoulder and offering advice as you learn the hobby.