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    Re: Celestial Navigation Class.
    From: George Brandenburg
    Date: 2010 Jul 12, 15:38 -0700

    I've been a volunteer at the Salem (MA) National Maritime Site for a couple of years. Along with several historic buildings, the Site is the home of the Friendship, a replica of a three masted East Indiaman from the early 1800's. My "job" there is to serve as a resource person on celestial navigation and our local hero, Nat Bowditch. Last month I did a training session for the rangers and Friendship crew on both of these subjects. Obviously with only an hour and a half I couldn't do either justice, but my hope was to give them enough information so that they could make informed comments (and maybe demonstrate the use of a sextant) when taking tourists around on the ship. Up till now navigation had pretty much fallen through the cracks on these tours. I received a lot of positive feedback from the participants, and some visitors are now getting a nav spiel on the ship.

    In the case of Bowditch I wanted to give a brief summary of his life (for those who hadn't read Carry On Mr Bowditch). I also wanted to give some insight into his navigation contributions. As for navigation my intention was to give them a feeling for why and how celestial navigation works, and to give an overview of how a ship like the Friendship would have used it to improve upon dead reckoning. I am indebted to Frank and his course on 19th Century Celestial navigation this March, not only for the celestial navigation part, but also for insight into what Bowditch actually did.

    As an added feature, at the end of my talk I showed a GoogleEarth animation of the maiden voyage of the Friendship from Salem to Batavia (now Jakarta) in 1797-98. To do this I spent an afternoon in our Phillips Library transcribing the lat/long coordinates from the 200-year-old captain's journal into a spreadsheet. I then used the www.earthpoint.us website to convert the coordinates into a GoogleEarth readable file.

    In any case I have posted all the materials associated with this training on the web, and I'm posting this message in case any NavListers might be interested. Below is an annotated list of the posted files.

    George B


    PDF Files:
    BowditchCelNavTalk -- My training talk slides.
    Celestial Navigation Primer -- Talk backup with more details (again thanks to Frank for most of this).
    Bowditch and the NAPN -- More backup information.
    FrienshipAlmanacIntro -- Instructions for demonstrating sextant sun sights on the ship.

    Excel Files:
    NOAA Solar Position Calculator -- A complete self-calculating solar almanac.
    Solar_Sight_Calc -- I wrote this using the NOAA code for use on my iPhone (using the Sheet2 app).
    It calculates lat for a noontime sight or long for a morning/afternoon time sight.
    Friendship_Almanac -- This is a daily sheet for use with sextant demonstrations on the ship (see PDF file).
    (This "Almanac" is something of a cheat - it assumes local lat and uses EDT+4 as GMT.)

    GoogleEarth File:
    FriendshipMaidenVoyage.kmz -- This should work fine once you have GoogleEarth downloaded.
    Press the play button to see each day's logged position (set the speed slow).
    The occasional lunar longitude determinations are shown by red stars.
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