Dead Reckonings

I’ve been fascinated by astrolabes for a very long time, roughly 20 years. It was this avocation that led to my interest in sundials and, because they share museum space, my interest in clocks. When I lived in Rockford, Illinois, I would haunt the Time Museum, an institution that produced the most beautiful book on astrolabes. Adler Planetarium in nearby Chicago has one of the best astrolabe collections in the entire world, producing another beautiful book solely on Western astrolabes and a gorgeous book on antique scientific instruments in general. None of these provide the mathematical details of astrolabe design beyond a description of stereographic projection, and indeed this kind of detailed information is rarely found. The Astrolabe, a new book by James E. Morrison, is an absolutely unique and wonderful book on the mathematics needed to create accurate, beautiful designs of astrolabes, quadrants and other related instruments. I can’t recommend it enough to those who share the interests of this blog.

In 1996 I discovered James Morrison’s excellent website, still the best one on astrolabes, and ordered both versions of The Personal Astrolabe, a precision astrolabe on laminated card-stock customized for my latitude and longitude. Its 50-page booklet is excellent in explaining the basics of astrolabes and their use. I’ve used one of these astrolabes on camping trips to identify stars and tell time, and from that day to this, through 3 jobs, the other one has been hanging on my office wall. I’ve assembled and used two instructional astrolabe kits, one put out by the National Maritime Museum in Greenwich and another lesser one. I’ve devoured papers on dating astrolabes from variations in star locations due to the Earth’s precession, on detecting forged astrolabes, on Islamic astrolabe decorations, and so forth. So I like astrolabes.

And in the same year of 1996 Mr. Morrison sent me a draft copy of his translation of Henri Michel’s Traité de l’Astrolabe, the only text on the mathematical details of astrolabe design I had encountered other than the short appendix of Harold Saunders’ book, All the Astrolabes. But the constructions in Michel’s book were geometric; the only equations were provided in two chapters inserted by Morrison. In an accompanying letter Morrison mentioned that he was working on a book—and now, suddenly, 11-1/2 years later, here it is. And it is a stunning, 437-page, large-format book containing 265 detailed drawings from PostScript files created by the author, presenting the design and mathematics of astrolabes, quadrants and related instruments. In addition to the technical details, the book is infused with the history of these instruments, describing their global spread from Greek mathematical and astronomical thought through their maturation in the Islamic world followed by their re-introduction into Europe by the Moors in Spain, as well as presenting the origins and inventors of specific instrument types. A clear overview of astronomical basics is included for those with little background in this area. Program listings are provided in BASIC and C to calculate typical design parameters, and there is even an introduction to generating PostScript output for astrolabe graphics (I will be using LaTeX and the TikZ vector drawing package, thank you). I am thrilled by this book—it eclipses any other book I’ve seen on how to design astrolabes. It also provides specific examples on using these instruments—for example, this is the only book that I know of that describes how to use a linear astrolabe in sufficient detail for me to understand it.

You can find more information and a sample chapter from the book to download here (you may recognize Gunter’s quadrant in this chapter from Part III of my nomography essay). Morrison writes that he is from a family of grammarians, and it shows in the care and clarity of the prose in this book. If you want to see photographs of astrolabes you will want a different book; if you are interested in astrolabe design you will love this book.

To be clear, I have absolutely no financial connection with James Morrison beyond my purchases in 1996 and the Christmas gift of this new book from my brother. I also have no connection to Amazon or to the Adler Planetarium.

This entry was posted on Wednesday, January 16th, 2008 at 1:20 pm and is filed under books, astronomy. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.