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    Re: "d" corrections
    From: Stan K
    Date: 2016 Dec 6, 18:42 -0500

    Any of the planets inside Earth's orbit exhibit retrograde motion, so can have a negative v value.  Those planets are Mercury and Venus, but Mercury is not a navigational planet and is not listed in the Nautical Almanac.  So, of the navigational planets, Venus does have the monopoly.


    -----Original Message-----
    From: Mike Freeman <NoReply_Freeman@fer3.com>
    To: slk1000 <slk1000@aol.com>
    Sent: Tue, Dec 6, 2016 6:30 pm
    Subject: [NavList] "d" corrections

    Just trying to learn celestial navigation out of interest rather than necessity.
    I think it is important to identify the method I am trying to learn. I have a book, Celestial navigation for yachtsmen, Mary Blewitt. It uses the Nautical Almanac along with AP3270 and has printed a few sample pages in the book. It makes clear the v corrections are nearly always additive except Venus which is sometimes negative. One of the sample pages from the NA does in fact have negative v corrections for Venus. I think I understand the v and d corrections are required to accommodate acceleration & deceleration of heavenly bodies. If there was no acceleration or deceleration there would be no v or d corrections, only incremental corrections? The book says d corrections need to be applied in accordance with the general trend in declination. In the case of Venus the v corrections are sometimes applied contrary to the general trend in GHA.
    What I am wondering is in the world of v & d corrections has Venus got the monopoly when it comes to having corrections contrary to the general trend in GHA or declination.
    Look forward to reply.
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