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    Re: Lunar mechanics and Double Alts.
    From: Herbert Prinz
    Date: 2003 Apr 30, 12:19 +0000

    George Huxtable wrote:
    
    >
    > Finally I have a comment about what Herbert Prinz said, as follows-
    >
    > >In order to properly perform an LD using observed altitudes, we need
    > >four(!) officers on deck. Short of that, we have to cheat.
    >
    > I am aware that Herbert was saying that in order to make a point. But I
    > would not like readers to get the impression that there's anything
    > impossible, or "cheating", or even very difficult, in the job being done by
    > one man, if he is good at it. The navy ritual may have called for four
    > officers, but there are many examples of a single observer taking valid
    > lunars, right up to the days of Joshua Slocum. I don't think Herbert wished
    > to imply that one man couldn't do that job, but his phraseing above may
    > have given that impression.
    >
    
    I agree with George Huxtable that my wording could lead to a misunderstanding.
    Also, I exaggerated by 33%. Let me try again.
    
    First I shall revise the numbers. The 4th man reads the watch. Although he is
    essential to the process, if the result of the LD is to be of any practical
    consequence for handling a ship, the watch is of no relevance to the
    mathematical problem. So we will forget him. The simultaneous observation of
    the lunar distance and two altitudes without a watch will give the
    instantaneous position of the observing team at the moment of observation. This
    is sufficient to establish, say, the position of a surveying mark on land.
    
    Now let me re-phrase:
    
    "In order to classify an LD procedure as one based on strictly "observed
    altitudes", we need three observers. If we do not have three truly simultaneous
    observations (1 distance, 2 altitudes) we are cheating when we call the
    altitudes that enter the reduction 'observed'. "
    
    By no means did I want to imply that one man cannot "do the job", or is
    cheating if he does so. But he would be cheating if he claimed that he can take
    three simultaneous sextant observations all by himself. I used the word
    "cheating" with regard to the classification of the procedure, not its
    validity.
    
    Herbert Prinz
    
    
    

       
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