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    Re: Self Taught Celestial
    From: Lu Abel
    Date: 2013 Feb 28, 10:51 -0800
    Paul:

    I've been lurking in the background a bit on your thread, but it seems to me that you're doing things just right.

    1.  There's the thrill of doing your first sight reduction.   I remember mine -- was part of a class, we took some sights and then we retired to a nearby restaurant and our instructor helped us reduce them.  When my first shot produced a LOP only a couple of miles from our known location, I felt like Christopher Columbus (okay, no flak from the list that Columbus didn't do celestial; I didn't know that at the time).

    2.  Plastic sextants are fine for learning.  Okay, they don't have the absolute accuracy of a metal sextant, but if your goal is learning celestial and not getting fixes to a nautical mile or less, they're fine.  I do find, though, that they have a bit of lash in the micrometer drum, so take your sights (bringing body down or bringing up to the horizon) the same way you measured IE.   And one of these days, depending your money and enthusiasm, you may want to upgrade.  But it's not mandatory.

    3.  The iPhone app is great for reducing sights for learners.   I think the thing that's daunting about celestial is the large number of steps required to obtain a LOP.   First those required to determine LHA and Dec of a body and then those required to calculate Hc from them by traditional tabular means.  Being able to do the Law of Cosines on a calculator (or iPhone app) is a great way to split your learning process into two easier-to-swallow steps.  As you build on your skills, maybe learning tabular sight reduction (NASR, HO229, or whatever) may be in your future.

    As you have either already observed or will soon discover, this list is made up of many, many smart people.   Some are interested in the history of celestial navigation.   Some are interested in its future.   Some are traditionalists (the strongest of whom declare they will never trust GPS).  These may be the folks who suggest that you can never learn celestial without a metal sextant.   Or that the only way to reduce sights is by some tabular method.   Ignore them, keep learning, and welcome to the wonderful (if somewhat obsolescent) world of celestial!

    Lu Abel


    From: Paul Fithian <pcfithian@gmail.com>
    To: luabel@ymail.com
    Sent: Thursday, February 28, 2013 10:06 AM
    Subject: [NavList 22530] Re: Self Taught Celestial


    Thanks for the suggestion on the USNO sight, but that is why I listed the iPhone App, Sight Calc. It does the sight reduction by inputing LHA, Lat, and Dec. It outputs Hc and Z.
    I have the Timestamp App to record immediatly the time the Hs sight was taken. But I do plan to get an accurate watch so that I don't have to depend on a working iPhone.
    It is clear to me that using either the Sight Calc App or scientific calculator method for determing Hc and Z are way easier that trying to use any of the sight reduction tables. I can use my 25 year old HP for the calculations.
    But I am committed to learning the sight reduction technique in Kolbe's book (described as, "a version of the "NAO Sight Reduction Tables" as used in the Nautical Almanac since 1989) so that Kolbe's LTA becomes the only book I need to carry on board. The other methods of sight reduction should be unnecessary, as I don't plan to carry any of them on board. Right?
    The reality of all this is that CN is a fascinating subject that I've always wanted to learn. After reading Annie Hill's "Voyaging on a Small Income" where they describe navigation by sextant, I figured I could learn about this while it is still winter instead of watching TV.
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