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    Re: Why are NA sight reduction tables not popular?
    From: Gary LaPook
    Date: 2012 Apr 8, 15:17 -0700
    I agree completely!

    When they first included these tables in the N.A. I thought "neat" so I started working a problem with them. As I went along I said "WHAT?" .....then "HUH"...then "what the.."   then finally I said "why the hell would somebody come up with such a complicated was to do this computation?" I never tried them again. I still wonder why they came up with such a complicated new table when perfectly good short tables had been available for many years and could have been included in the N.A. instead, Ageton is only about 10 pages longer as is Weems (I prefer Weems) and either is much easier to use. So here  is my advice, use a razor blade to excise the tables from your N.A. and duct tape Weems (or Ageton)  to the back cover.

    Back in 2009 I compared the various short table computations which are found at these links. It would be interesting if somebody would do the same computation with the N.A. tables and post it for comparison.


    http://fer3.com/arc/m2.aspx/Fw-Chichesters-Calculations-LaPook-dec-2008-g6700

    Correction, since Chichester added his watch error of 2:30 his watch
    was running slow, not fast on GMT.
    


    http://fer3.com/arc/m2.aspx/Fw-Chichesters-Calculations-comparisons-sight-reduction-LaPook-dec-2008-g6760

    http://fer3.com/arc/m2.aspx/Fw-Chichesters-Calculations-SineCosine-method-LaPook-dec-2008-g6707

    http://fer3.com/arc/m2.aspx/Fw-Chichesters-Calculations-SineCosine-method-LaPook-dec-2008-g6720

    http://fer3.com/arc/m2.aspx/Fw-Chichesters-Calculations-SineCosine-method-LaPook-dec-2008-g6744

    http://fer3.com/arc/m2.aspx/Fw-Chichesters-Calculations-SineCosine-method-LaPook-dec-2008-g6745

    http://fer3.com/arc/m2.aspx/Fw-Chichesters-Calculations-SineCosine-method-LaPook-dec-2008-g6785


    gl

    --- On Sun, 4/8/12, Robert Eno <enoid@northwestel.net> wrote:

    From: Robert Eno <enoid@northwestel.net>
    Subject: [NavList] Re: Why are NA sight reduction tables not popular?
    To: NavList@fer3.com, NavList@fer3.com
    Cc: geoffreykolbe@compuserve.com
    Date: Sunday, April 8, 2012, 8:27 AM

    Apologies if this gets sent several times. My system is having problems with responding to this list.
    -----------------
    I'll wade in here once again. This topic was discussed a few years ago
    wherein I made the same comments.

    I'll preface my comments by stating that I have practiced astro-navigation
    since 1983 so I am not a neophyte. Not an expert either: just a
    well-practiced old codger. Now on to my comments:

    Back in 1990, I was summer stupid (summer student) working with a scientific
    research party near the Beaufort Sea. I had gone back to college relatively
    late in life to pursue a different career. Anyway, we were going to be in
    this field camp for 3 months so I took along my sextant, tables and other
    accouterments, knowing that I would have plenty of spare time on my hands;
    so why not use it to hone my skills.

    During this time, I tackled the tables at the back of the NA. I spent hours
    trying to master them and ended up hating them. Why?  I found them to be too
    complex in that there are too many steps; too much transposing and mixing
    and matching of numbers.   Even after I had come into a groove with these
    tables, I found I was still making stupid mistakes - blunders. I came to the
    conclusion, from a personal perspective, that these tables simply were not
    trustworthy enough if I found myself in a tight situation. Not that the
    tables weren't trustworthy, but that I could not be relied upon to employ
    them without the possibility of blunders creeping into the equation.

    The ostensible reason for having these tables is that they will be a back-up
    in the event of an emergency. And in an emergency, stress levels are  high.
    The last thing a navigator needs under such conditions, is a set of sight
    reduction tables that, due to the design, are prone to user blunders. During
    times of stress, a navigator needs a sight reduction system that is simple,
    fast and has a minimum number of steps.

    In my humble opinion, the best short system, notwithstanding the "forbidden
    zone" is HO 211 - Ageton. With a proper sight reduction form, Ageton is
    fast, easy, reliable and less prone to the generation of blunders. My all
    around preferred method is the spherical triangle formulas with a scientific
    calculator.

    I will admit here that I have never been great at math. It is a subject that
    I have always had to work hard at to master and this may be part of the
    reason why I found the NA tables to be tedious and difficult. As I
    understand it, the NA tables were developed in part by the late Admiral TD
    Davies who was, by all accounts a brilliant mathematician and a brilliant
    man all around. Regrettably, not all of us -- yours truly included -- are so
    conferred with genius. What is elementary to the luminary may be well above
    the heads of the average navigator. We have a lot of intellectual
    heavyweights on this list for whom the finer points of mathematics is second
    nature. But it should also be understood that traditionally, the average
    navigator only concerns himself with the end result: finding his location as
    quickly and easily as possible.

    So there is my two bits' worth. From the perspective of a practical
    navigator sitting in the cheap seats. Fire away boys.

    In the early 1990's, Greg Walsh, who was the editor of Ocean Navigator
    Magazine, wrote a rather scathing editorial about the NA tables, suggesting
    that they were too complex and should be removed from the NA in favour of
    something simpler. The response from one of the board members of the
    Navigator's Newsletter (I believe it might have been Doug Davies but cannot
    remember for sure) was priceless: In addition to countering Mr. Walsh's
    contention, the letter writer suggested that Mr. Walsh's comments were more
    worthy of something that had been "written from a barstool".

    Robert


    ----- Original Message ----- From: "Geoffrey Kolbe" <geoffreykolbe@compuserve.com>
    To: <NavList@fer3.com>
    Sent: Sunday, April 08, 2012 2:04 AM
    Subject: [NavList] Why are NA sight reduction tables not popular?


    > Frank said that he didn't know anyone who liked them (or words to that effect).
    >
    > Given that the NA tables  system is taught in Power Squadron navigation classes, I would have thought that the biggest hurdle of any system - becoming familiar with the method - would have been overcome and made this method popular.
    >
    > The NA sight reduction system has the advantage of being angles all the way, so you are not changing in and out of logs, and once you get the hang of it, this method seems to be as quick as any.
    >
    > Any thoughts on why it is not popular?
    >
    > Lu Abel says that the "Law of Cosines" is what is being taught to the Power Squadron these days as the principal method of sight reduction. I went and had a look at the Power Squadron website and sure enough, in the 'Nautical Tools' section, there is a handy little online sight reduction program, showing the formulae used - and presumably taught in Power Squadron classes.
    >
    > Now, there may be good reasons why the NA sight reduction tables are not popular, but as was pointed out some years ago by Herbert Prinz, the formulae given in the NA for sight reduction using a calculator are the best formulae available for a number of reasons and I am surprised that the Power Squadron do not teach those instead. The formulae for Hc is the same, but the Power Squadron formula for Zn blows up in polar regions, whereas the NA version does not.
    >
    > Geoffrey
    >
    >
    >
    >
    >
    > __________ Information from ESET Smart Security, version of virus signature database 7036 (20120407) __________
    >
    > The message was checked by ESET Smart Security.
    >
    > http://www.eset.com
    >
    >
    >


    __________ Information from ESET Smart Security, version of virus signature database 7037 (20120408) __________

    The message was checked by ESET Smart Security.

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