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For what it's worth, I would invite attention to the older method used to
compute the intersection of position lines, as set forth, at least, in
the older editions of Bowditch. Before the advent of cheap plotting
sheets, this method was considered standard with the time sight. It
really should be quite easy to program to calculator use and to avoid the
need for any plotting. I'm rather surprided that someone hasn't brought
this up before - perhaps there is something on it in the archives. In the
"old days" of navigation, one did not mark up charts or spend a lot of
money on new fangled plotting sheets, especially in the Merchant Service
where every penny was counted. Also, long before the USCG screwed up the
Licence examinations, which at that time took from eight to ten days to
complete, the Steamboat Inspectors looked favorably on candidates who
worked the older methods and didn't bother them by asking for plotting
sheets and short tabular compilations. Just a thought on methods perhaps
long forgotten ....

Henry

On Thu, 8 Jun 2006 02:12:19 EDT Frank Reed  writes:
> Guy wrote:
> "a computer plot LOP's with  Excel"
>
> There are ways, sure. I can think of at least two. I can also use  a
> wrench
> as a hammer! Can you describe why you want plots like that?
>
> Here's one way: calculate your LOP's "a la Sumner". That is, you fix
> two
> latitudes and calculate two longitudes from them for each sight.
> That gives you
> two points on each LOP. The points determine a slope and a starting
> point.
> Then  fill out two columns with points on those lines based on the
> slopes and
> starting  locations. An ordinary x-y line graph of the data will
> cross your LOPs.
> Throwing  in some x-y gridlines and other formatting will let you
> read off
> the fix, and  the result should print out nicely, too.
>
> "or other standard  software."
>
> Can you code? Even a very light version of Basic can usually  do
> nice LOP
> plots with a lot more versatility than an Excel  graph.
>
> -FER
> 42.0N 87.7W, or 41.4N  72.1W.
> www.HistoricalAtlas.com/lunars
>

   

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