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    Latitude by Noon Sun for Beginners
    From: J Parsons
    Date: 2009 Apr 28, 08:49 -0700

    I've been following with great interest, if with less than complete 
    comprehension, the recent threads on finding position at and around noon.
    I'd like to divert a tiny new rivulet from that stream-- a back-to-basics 
    thread on noon sights for latitude. I don't like those titles for how-to 
    books that end in "...for Dummies," so I'm using the kinder term "...for 
    I've been working the latest Nav Problem in Ocean Navigator magazine, and I'm 
    finding I can't get the latitude the editor does from the noon sight data 
    presented.  My main stumbling block seems to be that the time given for the 
    shot is not the time I consider Local Apparent Noon for the DR longitude 
    used.  Wouldn't that be essential?  If the sun is observed at 12 minutes or 
    more after LAN, how does one account for that difference?  
    My main source of instruction is Dutton's (12th edition), which I find usually 
    gives excellent and thorough explanations of procedures.  The article on 
    latitude by noon sun focuses on how to determine LAN and what to do with the 
    Ho obtained then.  I've found nothing so far about accounting for a time 
    difference and the fact that the sun is not at its zenith when observed 
    before or after LAN.  Much is made of combining the vessel's change of 
    position east or west with that of the sun to pinpoint LAN, but the magazine 
    problem provides no data about course or speed.
    I'll bet one you can tell me somnething that will make me slap my forehead and 
    exclaim "Of course!"  Fire away!
    Thanks in advance,
    John P.
    Navigation List archive: www.fer3.com/arc
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