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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.

gl

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 
publication.
>
> 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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