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    Re: Traditional navigation by slide rule
    From: Greg Rudzinski
    Date: 2016 Sep 25, 11:35 -0700


    How are you progressing with the Navigation 10" slide rule proto type?  I have been doing sight reductions with a K&E 4070-3 and noticed that the ST scale ends at 35'. I think an additional ST scale continuing from 35' would be useful when doing the sine product (classic formula) when declinations or latitudes are less than 35'. 

    Of late good slide rule results (1' precision) have been obtained with the K&E 4070-3 on morning low altitude Sun obs. (below 15°) and evening twilight Venus below 15°. Low altitude stars have been reducing  nicely also although not as precise (2' precision) when the azimuth is southerly.  When very near the meridian it is quicker and more precise to switch to the ex-meridian reduction formula.  

    Greg Rudzinski

    From: Bob Goethe
    Date: 2016 Jan 24, 21:20 -0800

    >>I think the problem with the pictured degrees-minutes scale is that it has 4 different heights of lines<<

    I agree with you, Bill.  I have been cooking up various line heights...and I think it is possible to do a good job on this, one that will make the rule legible.  I am a little surprised that some of the regular manufactuers in the golden age of slide rules didn't work a bit harder on that very issue (particularly for those rules that WERE set up in degrees and minutes).



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