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    Re: sextant without paper charts
    From: Lu Abel
    Date: 2008 Oct 30, 10:56 -0700

    I suspect we are actually closer in viewpoints than you may think.

    First of all, I was reacting to an earlier post where Scott seemed to assume that because a just-launched submarine carried a sextant, it would also be carrying copies of Ho229.  Given that space on a submarine is at a premium and that all six volumes (which it would need to carry) take up more space than is allocated to the average enlisted sailor for all his personal belongings, I had to wonder why one would do that rather than rely on a calculator.

    When I learned celestial, I learned it using 229 for sight reduction (I think scientific calculators were just coming out at prices that rival today's prices for 42" HDTVs).  With a courses in numerical analysis under my belt as a result of a graduate degree in computer science, I think 229 is brilliant.  The requirement for an assumed position which makes the LHA an integral number of degrees reduces the size of 229 by a factor of 600(!).  And I understand how and why double-differences are needed (when the second derivative of the function becomes significant and linear interpolation is no longer accurate).

    At the same time, I've had the opposite experience you had:  I didn't find 229 giving me insight, just "follow the instructions and the answer will fall out" (although with my understanding of graduate numerical analysis I could figure out what was going on).  On the other hand, perhaps because I am old enough that spherical trig was part of my high school math curriculum, I suddenly found the calculator formulas reviving long-ago learned math and found it reasonably easy to understand the formulas.

    Different strokes for different folks, I guess.

    And, yeah, I own a sailboat.   Getting there is all the fun.   BTW, I just read about a collision in Buzzards Bay, Massachusetts where a 59' foot sport fisherman rammed a sailboat, killing its skipper, because the skipper of the sport fisherman was busy entering waypoints in his GPS.   I've seen way too many skippers so entranced by their electronics they forget to look up and around, not only because it's required by the Nav Rules, but because that's why we're out on the water in the first place!!



    Bill wrote:
    Lu Abel wrote:
    I guess I have to wonder why anyone would use HO229 these days when for about
    $15 you can buy a solar powered scientific calculator (so no batteries to go
    bad, mine claims it will work if there's enough light for me to see the
    display) and therefore not have to go through the error-prone task of a HO229
    sight reduction when one can just solve the celestial triangle directly with a
    I can only speak personally.
    For me it was a starting point (I recall you were on the list during my
    cardboard-sextant days) when the idea of doing spherical trig was beyond my
    imagination. Doing it the harder way was a great learning experience, and
    viewing the numbers laid out in front of me I was able to see a pattern
    emerge that transformed the usual plug-and-chug spherical-trig equations
    from magic to tools.
    Another feel good is why we do cel nav at all, and why some on the list
    focus on the history.  It is fun. It is a connection to the old ways and the
    universe. If you are really using cel nav to get around, why stop with a
    pocket calculator?  Go whole hog and get a dedicated unit. A sextant and a
    couple of digital watches and you are good to go. Electronics never fail.
    But you know all of that ;-)
    On the other hand, if you have a watch or two, a sextant, an NA and a globe
    you are good anywhere.
    If my hobby is ever reduced to driving a twin-engine, twin-screw boat by
    electronics on the Great Lakes I will give up boating.
    Bill B.

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