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    Re: Greenwich date and time?
    From: Stan K
    Date: 2017 May 9, 10:35 -0400
    Mike,

    I have a couple of Blewitt's, but not the Tenth Edition, so I will have to work from your description.

    The only thing I am pretty confident of is that zone description (ZD) is -10.  With the convention that western hemisphere zone descriptions are positive and eastern hemisphere zone descriptions are negative, you can use the mnemonic "Follow the sign to Greenwich."  Applying the watch error first, then the ZD, I get:

        WT  03-44-15    7 Dec
        WE  (-)       5
        ZT   03-44-10    7 Dec
            +24 h          -1 day
        ZT   27-44-10    6 Dec
        ZD -10        
        UT  17-44-10    6 Dec

    The GHA of Aries values you show for 17h on 6 December and 7 December are correct, so I would like to believe it is just a transposition error in the book (12.3 vs 13.2), rather than an error with the date.  Unless, of course, I made some other mistake.  However, there are so many editions of Blewitt, and they apparently all seem to use different examples, so I can see an error like this slipping through.

    Stan


    -----Original Message-----
    From: Mike Freeman <NoReply_Freeman@fer3.com>
    To: slk1000 <slk1000---.com>
    Sent: Mon, May 1, 2017 1:50 am
    Subject: [NavList] Greenwich date and time?

    To assist on this occasion it might be handy if you have a copy of Celestial Navigation for Yachtsmen Mary Blewitt Tenth Edition ref page 46. However I will try to explain my confusion......
    Star sights 7th Dec 1990
    Time given as Standard time +10.  It is clear this is time zone -10 from DR N40 E153 and from following examples.
    7 examples given but I refer to only 1 
    Calculation for GHA Aries
    Quote from book.... "Standard time correction and watch error for all sights + 10h 5s"
    Watch  03h 44m 15s
    UT       17h 44m 10s
    GHA Aries  331 12'.3 + increments
    Above GHA Aries is correct for 7th Dec UT 17h however having applied correction for zone time & watch error at Greenwich it is not yet 7th Dec. It is in fact still 6th Dec. In which case GHA Aries for 6th Dec UT 17h is 330 13'.2. I may be unaware of a convention here. Maybe it is correct to anticipate and indicate the date after the zone time correction? Perhaps it is a mistake in the book? Perhaps navigators have their own way of doing things?
    Look forward to replies
    Thanks
    Mike
       
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