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    Time Sights
    From: Chuck Griffiths
    Date: 2002 Jan 29, 11:33 AM

    First, bravo to Mr. Huxtable for his very lucid, learned, lunar distance
    dissertation. I'll work the examples this weekend.
    
    Looking forward to his part 3, I have a couple of thoughts about time sights.
    First, have others besides myself noticed the frequency with which this term is
    misused? In my mind, a time sight is a method of finding one's longitude by
    solving the navigational triangle for meridian angle knowing codeclination,
    coaltitude, and colatitude. I've noticed several writers using the term for
    something else as the original time sight falls into disuse. I offer the
    following as an example:
    
        From Marine Navigation by Richard R. Hobbs 3rd ed. pg. 455
        "When a very high degree of accuracy in the latitude line is required, many
    navigators  construct a graph such as that shown in Fig. 25-2 (The figure shows
    altitude plotted    against time during a meridian sight.) to assist in picking
    the precise altitude of transit.    Such a series of sights is called a time
    sight..."
    
    I find this example interesting for two reasons. First, as mentioned previously,
    this is not my idea of a time sight. Second, Hobbs doesn't go on to describe how
    the resultant graphically determined time of meridian passage can be used to
    find one's longitude to produce a lat-long fix from the noon sight. Granted,
    it's not the best longitude fix, but if one goes to the trouble of graphing
    one's noon sight observations one might as well use it to the best effect.
    
    My second point for discussion is tables for solving real time sights. Bowditch
    (pre-1995) offers a history of such tables, sometimes referred to as horary
    tables, but I have never seen an example. Does anyone out there have an example
    of any of these that they could scan and post? I thought it might be a nice
    supplement to the discussion of finding longitude.
    
    Chuck Griffiths
    
    
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