navigating the old ways

Discussion in 'Education' started by lazeyjack, Jun 12, 2007.

  1. lazeyjack

    lazeyjack Guest

    In the hope of revitalising my lost skills, and picking up new ones, I would like to start a thread on navigating before the gps, before sat navs,before decca and loran, but after radar
    Kick it off my posting how to make compass deviation card
    swing the boat around the sun this is very handy for ships changing latitude and esp in the high lats of Artic circle, where the compass can do funny things
    You need first a pelorus, which is a fancy name for a card with 360 degrees marks, and on this card, which is clamped somewhere with 0 and 180 on ships cl, you need a pointer, arrow
    You also need the heavenly body, the sun, and two people, or any headland or mark over 3 miles away can be used, but at sea the only thing to use would be the sun
    You steam the boat in a circle, because the sun into far away, it makes no difference how big your circle is, then working around the compass(ships) you settle on the first heading, North, 000, and when you are on that course the other person calls the suns bearing
    , write this down and steer 15 more headings
    Add all the bearings together, and average out. the difference between the average will be the deviation east or west which are always equal each side of the line
    Easier to use circular notation
    Of course a pelrus is not necessary if you can sight over the steering compass
    what tables do you use for you sun, moon shots, Norries, or air sight reduction , almanac?
     
  2. charmc
    Joined: Jan 2007
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    charmc Senior Member

    Nautical Almanac: joint venture between HM Nautical Almanac Office and the US Naval Observatory Nautical Almanac Office.
     
  3. charmc
    Joined: Jan 2007
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    charmc Senior Member

    Small bit of trivia on the subject of traditional navigation: The US Apollo missions to the moon carried an "interplanetary" version of a sextant to enable them to plot a return course if all electronics failed.
     

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  4. lazeyjack

    lazeyjack Guest

    I aways used air sight reduction tables, but they expired in 2000
     
  5. charmc
    Joined: Jan 2007
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    charmc Senior Member

    Stu,

    Is the other person someone you don't like? 'Cuz having him/her look at the sun for azimuth can get nasty. :p :D

    The same source for the Nautical Almanacs publishes sun azimuths for given times and positions.

    I think you've got the swinging ship (or circling ship, which is probably a lot easier) technique down pretty well. Important skill, as, aside from the higher latitudes, there are some magnetic anomalies scattered all over this fair earth. One of the better known ones starts not far off the east coast of FL, although it's named for its northern terminus.
     
  6. lazeyjack

    lazeyjack Guest

    forget the az, can be any time, of day or night, if youa re in the NORTH, which brings me to the Mer Pass, i cant cos I have no boat and on my coast at zenith the sun is over the land, can you please rearrange this for me?
     
  7. timgoz
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    timgoz Senior Member

    I was taught using the 249(?) air sight reduction tables in conjunction with the Nautical Almanac.

    Tim
     
  8. lazeyjack

    lazeyjack Guest

    did you use plotting chats Timbo?
     
  9. charmc
    Joined: Jan 2007
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    charmc Senior Member

  10. charmc
    Joined: Jan 2007
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    charmc Senior Member

    I put in that request for you, along with my frequent request for great wealth and a Greek god body. Hope your request fairs better than mine have so far. :)
     
  11. timgoz
    Joined: Jul 2006
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    timgoz Senior Member

    LazeyJack,

    We used universal plotting sheets. I've redone the course 2 times since I first took it in 1991. Had a nice Heath Brit Navy sextant but it got stolen. :mad:

    As a besides the point, I have a Swiss Army pocket watch that has a rate of error of -1/25 sec. a day. Also have one of thier wrist watches that has a -1/15 sec error. Have to get one more if I'm ever going to put Celestial to use again.

    Of course good quartz timepieces were not available in the era you speak of.

    Tim
     
  12. lazeyjack

    lazeyjack Guest

    my fist ocean passage was a hoot, but the sense of accomplishment can not be equalled looking at a gps screen, to be able to say, "Kandavu will appear soon on the horizon" and then it does, it is always a thrill
     
  13. timgoz
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    timgoz Senior Member

    Magical even. :)
     
  14. charmc
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    charmc Senior Member

    You got that right! Always good to be able to say, "I did that myself". Too many folks today have no idea what that means.
     

  15. marshmat
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    marshmat Senior Member

    It makes me rather curious, now, to wonder just how many of the boaters and boats who routinely make trips based on electronics alone would actually be able to find their way home if the GPS ever crapped out. And how many would just float around, or better yet motor in wide circles, until they ran out of gas.
    On a different note- Just how precise do you folks like your astro nav timepieces to be, anyway? I'd love to learn astro nav but it's rather useless in the areas I usually traverse; ie. rivers and inland lakes. A few miles isn't close enough- even a few hundred metres isn't close enough- navigating Ontario lakes, especially in the dark, is a matter of learning to quickly match features on the chart with what you actually see, noting reference points with which to plot your course, etc- you're rarely beyond sight of land, so you need a feel for the lake's character and layout rather than for the stars and the compass.
     
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