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    Re: First plot!
    From: Joe Wong
    Date: 2022 Jun 20, 05:52 -0700


        Yes I'm a ship modeller myself and I has been building these miniatures for several years. As a total landsman, building these models could well be the only connection I have to a seafarer's life.

         I took three sights in total, one through the Kollsman, the other two through typical marine sextants and a Davis AH. Cant imagine how military navigators back in the day achieve such precise plotting in a shaky aircraft with vibration,noise,Coriolis effect and an extremely small field of view, you name it. I believe Al has made a small mistake in the intercept,since I did plot my intercept from the assumed position,which is 140°10′48″E(plotted as 140°11′E on the chart.),Hc value as calculated is 75°12′ by refering to HO249,Ho is 75°37′42″. AL has taught me in his post to round the HO figure down to whole minutes therefore HO is 75°38′. Direction is towards. Consistant with my plotting. 

        As for the Kollsman, I now believe that I was just pure luck by positioning the instrument in such a manner that the imperceptible slight difference between the true horizon and the bubble horizon happens to negate any prism error of a certain angle. If I have a surveying theodolite I'd definitely use it to check and note the instrument error on my Kollsman.


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