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    Re: Questions about Celestial Navigation
    From: Peter Monta
    Date: 2018 Sep 11, 03:52 -0700
    A good set of questions.  Here's my take on them:

    1. How popular is celestial navigation?

    At a guess, there might be a few tens of thousands of maritime practitioners worldwide who occasionally take celestial sights.

    2. How trustworthy is Celestial navigation as a main type of navigating?

    Its main limitation is the availability of celestial sources (whether or not the Sun, Moon, or stars can be seen in the sky).  Poor weather could prevent any new celestial data for days at a time, forcing the navigator to rely on dead reckoning (incremental updates using measured speed and course).  If the weather is good, though, the trustworthiness of celestial data is high, since the instruments and almanacs and computation are generally reliable.  (For longitude, a trustworthy source of time is needed, such as from a quartz wristwatch.)

    Position accuracy using celestial alone is on the order of a few nautical miles (a few thousand meters), good enough for blue-water sailing but marginal for piloting and landfalls, where the navigator would switch to more accurate local landmark-based techniques.

    3. What type of technology is used in Celestial Navigation?

    Angle measuring instruments (sextants), almanacs/ephemerides (and the technology tree that produces them), computation aids (ranging from trig and log tables in book form to calculators to small computers), clocks (historically called "chronometers").

    4. What type of people are involved with Celestial Navigation?

    Sailors, astronomers, hobbyists/enthusiasts, historians.

    5. Currently, how much do we as a population know about Celestial navigation?

    I don't know, but I think that most people are familiar with the concept of "navigating by the stars", even if the details are unfamiliar.

    6. How accurate is this knowledge?

    The general concept of "navigating by the stars" is accurate, as far as it goes, in the sense that such navigation is possible.

    7. What sort of techniques are used in celestial navigation?

    Generally, angles are measured between celestial bodies and the sea horizon.  These angles, together with the time of observation from a clock and the almanac data computed in advance by astronomers, can be processed to yield location information.  With "old navigation", up until about 1870, separate techniques were used for latitude and longitude/time.  After 1870 they were combined into the more general "lines of position".

    8. Do you know of any techniques that were developed from the Polynesians?

    I don't know of any.

    9. How much to you know about Polynesian celestial navigation?

    As far as I remember from various accounts in books, they used stars for steering/azimuth references and possibly latitude (using kamal-like aids? plumb lines?) and were adept at reading the sea state (such as swells and birds).  I think they also had quipu-like maps.

    > "How has our knowledge of the Polynesian Celestial Navigation system helped to develop modern Star based navigation"

    Polynesian navigation is interesting, but I don't think there has been any connection with modern techniques.  I believe there was some contact between the main drivers of modern celestial navigation, 18th and 19th-century Europe (principally British and French), and the Polynesians.  Cook's expeditions would have been in the right time and place for example.  But my impression is that this contact engendered some admiration for the audacity of Polynesian voyaging, but no significant technology transfer.

    Cheers,
    Peter
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