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    Review: "The Naked Nautical Sextant"
    From: Frank Reed
    Date: 2009 Mar 9, 14:41 -0700

    Review: "The Naked Nautical Sextant and its Intimate Anatomy"
    Last week, the President of the Florida Senate opened the latest session of 
    that legislative body with a symbolic gift for every member: a sextant in a 
    wooden case. He expected Florida state senators to look to this symbol for 
    guidance in tough times, to remember that in the darkness, they can still 
    find their way... Is that all that sextants are today? Symbols? Echos of a 
    bygone era?
    Bill Morris, a retired engineer living in Pukenui, New Zealand, has recently 
    written a book entitled "The Naked Nautical Sextant and its Intimate 
    Anatomy," and for Bill sextants are anything but symbols. They are intricate 
    devices to be dis-assembled and re-assembled and brought back to life. They 
    are not just old navigators' tools, but scientific instruments capable of 
    amazing accuracy in the measurement of angles when properly cleaned, 
    restored, adjusted, and calibrated. Sextants are a bit obsolescent, yes, and 
    Bill admits that in his preface, but they are far more than symbols.
    Bill's "book" is an electronic book, delivered by download from his web site 
    at www.sextantbook.com for $24.95 (USD) or $32.95 when shipped on CDROM, well 
    worth the money in my opinion. This is certainly a book in terms of the scale 
    of the content within it. There are over 250 pages in fifteen chapters and 
    four appendices and over 200 color photographs as well as diagrams. Like 
    computer software, electronic books can be updated regularly if errors are 
    found with little or no cost to the end user. While reading Bill's book I did 
    spot a few little typos here and there, inconsequential things (for example, 
    the table of contents labels appendix 5 as appendix 4 and in the caption for 
    the frontispiece, a sextant is labeled as "unamed"), but by and large the 
    book has been carefully edited, and I would assume that any updates would add 
    content rather than correcting the few flaws in it. 
    Fundamentally, this is a "how-to" book. It is the summation of Bill's many 
    years of practical experience tearing down and restoring nautical sextants. 
    Read it and you will learn how to disassemble and re-assemble every component 
    of a standard nautical sextant. In addition, though he makes no claims of 
    detailed scholarship, the book necessarily includes extensive information on 
    the history of sextants and their basic optical principles, too. And as an 
    aside, there's an interesting section on the history and construction of 
    Ramsden's Dividing Engine which made accurate sextants possible. There's next 
    to nothing, of course, on wooden quadrants or more recent plastic sextants. 
    The book covers standard metal sextants, such as were made from the early 
    19th century through the latter half of the 20th century.
    "The Naked Nautical Sextant" offers excellent advice on tools and techniques. 
    Naturally, the author details the standard tools required: various sizes of 
    screwdrivers, non-magnetic forceps, vices, etc. and perhaps a pin-wrench (for 
    removing those little notched rings that secure lenses in telescopes), but he 
    also advises the would-be sextant restorer on inexpensive aids like small 
    sandbags to support the sextant on a work table. A great idea! According to 
    the author "Using just a few hand tools, the average person with the aid of 
    this book should be able to strip down a sextant to its component parts, 
    clean and lubricate them, put them together again correctly and adjust the 
    instrument." This stretches the concept of an "average person" a little bit, 
    but I think it would be fair to say that the "average person who might 
    actually pick up this book" would be abl
    e to follow the directions and advice and accomplish most of the claimed goals.
    There are a few little curiosities of style in the book. For example, Bill 
    writes in his preface (briefly commenting on modern electronic systems that 
    have largely replaced the sextant in practical navigation) that it is 
    possible "for several times the cost of a sextant, to buy a system that 
    provides the user in real time with her position on a chart of the area 
    through which she is passing." and then says in a footnote "I do not of 
    course intend to imply that there are no male navigators." I suppose that 
    this is an inside joke. 
    There are over 200 diagrams and photographic illustrations in the book. A few 
    could use some revision. For example, there's a numbered diagram of the 
    sextant components that would be clearer if the numbers ran in a consistent 
    order. All of the photographs are professional in quality and illustrate the 
    intended point beautifully. There's an excellent section in the book 
    describing the various sextant frames, their composition (brass versus 
    aluminum) and design. The photographs here are a real pleasure: there's 
    something delightful about seeing all of these familiar instruments torn down 
    to just the frame. It is indeed a collection of "naked nautical sextants". 
    Though there is plenty of information in the book for the beginner, much of 
    the advice here will also be interesting to those with significant mechanical 
    skill or engineering background. For example, with respect to severely 
    damaged screws, he notes that "taps and dies" are available "if you have to 
    make a new screw from scratch." 
    The book occasionally assumes some knowledge of tools and the language of 
    tools that may not be present. For example, we read, "This is a common 
    engineering solution when an accurate, shake-free fit is required between a 
    plug and a socket, seen most commonly in the Morse tapers of drill shanks. It 
    is not generally appreciated that the rectangular tang of such a drill plays 
    no part in transmitting torque." I was left scratching my head over that one. 
    Likewise, regarding certain shades, "The mountings are often not easily 
    dismantled as swaging may be used to fix the various parts in place." What's 
    swaging? Sure, I could look it up (and in fact, I did: see "swage" on 
    Wikipedia), but an inline definition of some sort or a footnote would help 
    here. The word turns up around ten times in the book.
    Sextants of many types and manufactures are covered. There are Husuns, 
    Tamayas... the US Navy Mark II, Heath sextants and Plath. The book includes 
    considerable practical detail on dis-assembling the popular Russian SNO-M and 
    SNO-T sextants. To his credit, Bill does not use the name "SNO-T" sometimes 
    found in accounts of Russian sextants ("CHO" consists of the Latin letters 
    which resemble the Cyrillic letters that are properly transliterated as SNO).
    I found the sections on the internal anatomy of the micrometer assembly and 
    bearings most interesting. These are components that most of us who have used 
    sextants take as given and rarely get to see dis-assembled and analyzed from 
    an engineering perspective. We can really see the generations of design that 
    went into these seemingly simple devices. Even the release catch, which 
    disengages the micrometer and lets the index arm swing smoothly, is analyzed 
    in great detail. The book also covers the tangent screws which provided fine 
    adjustment of the position of the arm in older vernier sextants from the 19th 
    and early 20th centuries.
    There are details on small parts like the mirror frames or holders and how 
    they were constructed in older instruments. A motto for this book might be: 
    anything that can be taken apart WILL be taken apart. And so we learn how to 
    dis-assemble a remarkable variety of mirror cells. This is encyclopedic 
    information, and most readers will probably skip over some of it to get to 
    the particular instrument that interests them. Even sextant shades are 
    discussed at length. "All the properties of absorption, reflection, 
    refraction and diffraction have been used by one maker or another in a 
    variety of shades" (diffraction? Did he mean polarization?). 
    The section on telescope optics is excellent, demonstrating a clear 
    understanding of the optical principles and the construction of the various 
    telescopes, monoculars, sighting tubes, as well as the various mounting 
    hardware and rising pieces. Bill provides a comparison of the wide variety of 
    solutions that sextant manufacturers have found over the decades. For an 
    example of practical advice, when cleaning old lenses, Bill warns "but beware 
    of soaking them in alcohol, as some of them are fixed with shellac, which 
    dissolves in alcohol." --Interesting. I didn't know that.
    Even sextant legs and handles get a chapter full of details! And it doesn't 
    stop there: the construction and carpentry of sextant boxes and cases is also 
    Chapter 14 feels like a change in editorial style, and if I didn't know that 
    this was the work of one author, I would almost think that this was a second 
    writer at work. Bill here finally addresses the philosophical issue of 
    restoring an old instrument. Should it not perhaps be preserved in its 
    original state? There are no simple answers to such questions, of course, and 
    overall, I think Bill makes a good case for an acceptable level of 
    restoration. It's in this chapter that you'll find most of the valuable tips 
    and tricks on general cleaning and restoration including advice on 
    re-painting the frame of an old instrument. This whole chapter feels more 
    like a journal or a "blog" than the rest of the book. There's really nothing 
    wrong with this by itself. It's still good reading and a goldmine of ideas, 
    but it seems to me that most of this material could have been re-worked into 
    other parts of the book.
    The last full chapter of the book describes sextant adjustment. It's a very 
    fine account of the methods found in any good navigation manual. It might 
    have benefited from a better discussion of the relative significance of the 
    various errors and could have included some mathematics. For example, the 
    author tells how to eliminate side error, but there's no mention of the fact 
    that side error is unimportant (except in certain methods for measuring index 
    error). Related to the general problem of adjustment and error-correction, 
    one of the four appendices covers the measurement of arc eccentricity and 
    error using collimators.
    So who's this book for? Who would buy "The Naked Nautical Sextant"? Anyone who 
    owns a sextant today is likely to perform a little basic maintenance on it. 
    And many modern sextant enthusiasts have yearned for the know-how to perform 
    a complete re-construction of an old sextant. This book provides all the 
    details you might ever want. But how about for those are "all thumbs"? If you 
    are not able to work with small precision tools, no book will cure you of 
    that. And yet there's vicarious pleasure here, even for those who will never 
    attempt to dis-assemble a sextant. As you read along, you feel a bit like 
    you're peering over Bill's shoulder as he works. For those who have already 
    dis-assembled and restored a sextant, who might perhaps suspect that they 
    know all this already, the most significant addition here will be the sheer 
    variety of instruments examined in their dis-assembled glory. It's not just 
    the intimate anatomy of one species of sextant -- "The Naked Nautical 
    Sextant" is a comparative anatomy of a whole zoology of sextants. I highly 
    recommend it.
    And incidentally, back to those "symbolic sextants" in Florida that I 
    mentioned at the start of this review... The total price, including an 
    engraving on the display box, was $32.50 per sextant, so I think we can 
    safely conclude that they were not real sextants at all, but rather those 
    gaudy display models --little better than toys-- that we see for sale on 
    auction sites on the Internet. Those Floridian senators do NOT need this 
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