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    Re: Arg 1 Ww 11 U Boat Navigation Device Ebay Item Number: 370193239339
    From: Gary LaPook
    Date: 2009 May 23, 10:01 -0700

    So the principle of the ARG1 is quite simple but to get results that
    are accurate enough for normal navigation the device must be made very
    precisely i.e. expensively. I'm not sure how easy it would be to be
    looking though microscopes while the ship or plane is in motion.
    The normal ten inch slide rule can produce results that may be usable
    for some navigation, far off shore or for emergency navigation, most
    navigators would prefer a method that produces results that are more
    consistently accurate. The Bygrave fills the bill nicely.
    On May 23, 3:45�am,  wrote:
    > In response to your request, I have attached the article on the ARG1 written 
    by David Charlwood in the Summer 2002 Navigator's Newsletter. Unfortunately 
    we were notified last summer that the Navigation Foundation was going to 
    close its doors since it remaining officer could no longer keep up the 
    > This entire article is contained in the attached ARG1-1 through ARG1-9 PDF pages.
    > In the same issue there was a another article by Robert Girder describing a 
    Great Circle Slide Rule that just happens to use the same method as the ARG1. 
    I have included his article as -10 through -11. His diagram is the same 
    equatorial stereographic diagram as that used in the ARG1 but not to the same 
    precision, you do not need a microscope to read it. However, we can use this 
    diagram to make a demonstration model of the ARG1 so see how it works.
    > I added some labeling of altitudes to the diagram as -12, cut it out, made a 
    hole in the center and mounted it on the center pin of my 2102-D Star Finder 
    base. I then took a clear sheet of plastic, punched a hole in it and mounted 
    it over the diagram and then used a scissors to cut off the excess material 
    around the edges. I then added an index mark, see -13.
    > I then worked the same problem as described in the article, declination 
    8?51' N, LHA 29? and latitude of 51?00'N. Since I did not have any 
    microscopes to set I simply set my index mark on the plastic sheet overlay to 
    90? and marked on the sheet a dot to represent the declination and LHA, see 
    -14. Obviously, this visually interpolated dot cannot be nearly as accurate 
    as the cross hairs in the microscope of the ARG1. I then rotated the index to 
    the 51? mark which then brought the dot representing declination and LHA to 
    the position on the grid showing the Hc and Az. See -15. I read out an Hc of 
    about 40? and an azimuth of 220? (40 plus 180 since I did not re-label the 
    azimuth scale on the diagram to avoid clutter.) This is pretty close to the 
    answer given in the article of Hc 41?34' and Az of 220?.
    > Hopes this helps.
    > gl
    > �ARG1-1.pdf
    > 315KViewDownload
    > �ARG1-2.pdf
    > 337KViewDownload
    > �ARG1-3.pdf
    > 294KViewDownload
    > �ARG1-4.pdf
    > 360KViewDownload
    > �ARG1-5.pdf
    > 268KViewDownload
    > �ARG1-6.pdf
    > 348KViewDownload
    > �ARG1-7.pdf
    > 154KViewDownload
    > �ARG1-8.pdf
    > 128KViewDownload
    > �ARG1-9.pdf
    > 104KViewDownload
    > �ARG1-10.pdf
    > 375KViewDownload
    > �ARG1-11.pdf
    > 228KViewDownload
    > �ARG1-12.pdf
    > 265KViewDownload
    > �ARG1-13.pdf
    > 261KViewDownload
    > �ARG1-14.pdf
    > 262KViewDownload
    > �ARG1-15.pdf
    > 260KViewDownload
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