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    Re: Refraction, sunset, and HO229 beginner question
    From: Jim Theriot
    Date: 2004 Jul 22, 09:46 -0500

    Bill said:
    
    > The idea struck me that at sunrise and sunset I could get a LOP without a
    > sextant.  One barrel of my binoculars, a heavy-duty neutral-density
    filter,
    > a watch, Nautical Almanac and HO229 tables would suffice.
    
    I was struck by a possibly similar idea -- I am not sure if it's the same
    idea,
    because Bill's comments are mostly about use of almanac and tables, not
    about
    the basic principle.  My idea was simply that for any observation you make
    with watch and sextant where the object appears on the horizon, the same
    observation could be made with watch only (or watch and binoculars).  Then
    you run the computations, using using zero for the sextant reading, making
    all
    the appropriate corrections (but using zero for the sextant index error
    correction!), and you should get identical results.  Possibly that's what
    Bill was getting at.
    
    Furthermore, it seems that on a moonless night you might be able to get
    a LOP from the setting of a star or planet more easily using this method,
    since you don't have to see the horizon, you only need to note the instant
    at which the star or planet blinks out.
    
    I wanted to test this theory on a sailing trip a couple of months ago (I
    live inland, not in sight of a 'real' horizon), but weather and
    circumstances
    prevented it.
    
    Regards,
    Jim
    
    
    

       
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