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    Equal altitudes problem of March 9
    From: Mal Misuraca
    Date: 1997 Mar 10, 14:47 EST

            The time of the last sextant observation in the column from the problem
    posted yesterday is in error.  The last time should be "22:09:05," instead of
            The nautical almanac data for observations of the sun on August 3, 1995 is as
    follows.  If you need GHA and dec for other exact times, you can either get it
    from the proper nautical almanac, from Celesticomp V or another computer
    source, or from the Interactive Computer Ephemeris ("ICE").  ICE was used to
    generate the following figures, and I will be happy to look up others and post
    them within a day or two of being asked.
            Time		GHA		Dec		
            21:09:05	135.438		17.271 N	
            21:19:05	138.138		17.270 N	
            21:25:00	139.434		17.270 N
            21:27:00	140.125		17.269 N
            21:30:30	141.050		17.269 N
            21:35:14	142.161		17.268 N
            21:39:00	143.126		17.268 N
            21:39:05	143.142		17.268 N
            21:39:10	143.151		17.268 N
            21:42:56	144.151		17.267 N
            21:47:40	145.176		17.267 N
            21:51:10	146.151		17.267 N
            21:53:10	146.451		17.266 N
            21:59:05	148.138		17.266 N
            22:09:05	150.438		17.265 N
            These times do not coincide in all cases with the problem you were given, in
    order not to make the problem too obvious in light of the almanac data.
    Nonetheless, if you cannot work the problem without other times' data, I will
            Thanks to the Net for the opportunity to explore this old system, which has
    now got a renewed and special appeal---for being very simple to teach, now
    that GPS makes many small vessel sailors impatient about learning celestial.
    This means equal altitudes may become, at least for my students, the salvation
    of a passage turned nightmare when a GPS failed, or simply a source of extra
    peace of mind and satisfaction, to know as Chichester said that celestial is
    good if only because "it is the one form of navigation not in the control of
    any government."
            I hope you will summon me for more information, if you feel you need it.
    Maybe you do, and maybe you don't.  (Hmmm.)
                                            Mal Misuraca

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