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    Re: Sight reduction method history
    From: Francis Upchurch
    Date: 2013 Nov 8, 11:23 -0000


    Thank you very much for that. Do you by any chance have instructions for use? I am hopeless at tables!

    I will reply to all the other helpful postings asap. Busy working right now!



    From: NavList@fer3.com [mailto:NavList@fer3.com] On Behalf Of Greg Rudzinski
    Sent: Thursday, November 07, 2013 7:48 PM
    To: francisupchurch@gmail.com
    Subject: [NavList] Re: Sight reduction method history



    Attached is a PDF of Robert Bernacky's modified Martelli Tables. Table V gives Local Hour Angle instead of time to facilitate deriving Longitude from GHA and LHA. I like this table for the simple reason that few mistakes seem to get made during look ups.

    Greg Rudzinski

    Re: Sight reduction method history
    From: Francis Upchurch
    Date: 2013 Nov 7, 02:44 -0800
    I've been following this fascinating string with interest. Cannot add much to the wisdom already shared, but Lu also asked about slide rules? I find the cylindrical Bygrave and Fuller, with very long spiral scales are usually accurate to 1-2' for sight reduction. the Bygrave is very quick, the Fuller,using the sine/cos formula takes twice as long, so I tend to use the Bygrave.The Fuller dates from early 1900s but I've never found evidence of use in navigation.Chichester famously used a Bygrave in his 1931 solo flight across the Tasman sea.Interestingly, he taught astronav to the RAF during the war and used the Air Almanac, never mentioning the Bygrave, which was clearly never standard RAF issue.However,the top "Pathfinder" navigator AVM Bennett apparently used one until the end of the war in preference to the Air Almanac. I find it much quicker and more fun than tables.I use the Fuller to clear my lunars, great fun!(but I generally check on Frank's site later.)
    I notice Frank briefly mentioned Martelli's tables? I had never heard of them, but by amazing coincidence have just been reading the book by one of my heroes Frank Pidgeon, Islander 1922 circumnavigation. On page 12 he recommends the Martelli tables as his favoured method to reduce his time sights. However, by page 17, he says that going below to do the maths made him sea sick, so from then on, stayed on deck and guessed a rough LAN time for longitude from his noon meridean sight! and so on , round the world!
    Can send details of slide rules on request. Best wishes, Francis Upchurch
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