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    Re: Formulas to Compute LHA
    From: Lu Abel
    Date: 2009 Jun 28, 09:15 -0700
    Will Ross, in a later post, mentioned the United States Power Squadron's celestial nav courses (there are two of them and they are more accurately "offshore navigation" classes, GPS and even computerized voyage planning have been added to traditional celestial).

    They have a well-organized sight reduction form that includes a time diagram.  

    You can download it at http://www.usps.org/national/eddept/n/files/sr96a.pdf    The front side includes all corrections going from hs to Ho, calculating the GP of the body, and then a Law of Cosines reduction to Hc.   The back side includes a form for calculating Hc using the NASR method.

    If you read Chapter 15 of Bowditch (available on-line), there is a pretty comprehensive explanation of how to draw a time diagram.   Or, as Will suggests, take the USPS course(s).

    Lu Abel


    Bill wrote:
    Andrew wrote regarding time diagrams:
    
      
    I am interested in this diagram,  where can I find it?
        
    
    I am not certain this is what you are looking for as it is not called "time
    diagram", but the attached does make LHA a bit more digestible for me. It is
    from Susan P. Howell's book "Practical Celestial Navigation" which I
    purchased from Celestair.  Other texts I own (but are sadly in storage far
    away) may use the same diagram but in the opposite rotation.  The end result
    is the same.
    
    A question for the list.  When teaching at Purdue I recall copies from a
    book could me made for educational purposes, and "deju duh" (the Indiana
    version of "deju du) causes me to think there was a limit on the number of
    copies.  Am I skirting violation of copyright law by postings excerpts? If
    so, would it be legal to send just one copy off list?
    
    Thanks
    
    Bill B
    
    
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