NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Weems LOP Short Table Method
From: Gary LaPook
Date: 2014 Jan 19, 12:32 -0800
From: Gary LaPook
Date: 2014 Jan 19, 12:32 -0800
I posted this back in 2009:
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"You might want to skip Weem's New Line of Position Book. I bought it because I liked the idea of having all the data for one latitude on one page, much like H.O. 214 and H.O. 249, since his first book is arranged like H.O. 229 by LHA. But when it came in the mail I didn't like it since it is so much bigger. He also introduces a new column of "Z" which can be used to calculate an approximate azimuth. I don't know why he included this column since this method is no easier than the method he already showed for computing azimuth using table "B" alone and it only produces an approximate azimuth so is not as accurate as the other method. I am attaching two photos of the two sets of tables. I have indicated the entries for latitude 20 degrees, LHA 11 degrees, just above the ruler."
From: Bruce J. Pennino <bpennino.ce@charter.net>
To: garylapook@pacbell.net
Sent: Saturday, January 18, 2014 8:23 PM
Subject: [NavList] Weems LOP Short Table Method
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"You might want to skip Weem's New Line of Position Book. I bought it because I liked the idea of having all the data for one latitude on one page, much like H.O. 214 and H.O. 249, since his first book is arranged like H.O. 229 by LHA. But when it came in the mail I didn't like it since it is so much bigger. He also introduces a new column of "Z" which can be used to calculate an approximate azimuth. I don't know why he included this column since this method is no easier than the method he already showed for computing azimuth using table "B" alone and it only produces an approximate azimuth so is not as accurate as the other method. I am attaching two photos of the two sets of tables. I have indicated the entries for latitude 20 degrees, LHA 11 degrees, just above the ruler."
See attached photos.
gl
From: Bruce J. Pennino <bpennino.ce@charter.net>
To: garylapook@pacbell.net
Sent: Saturday, January 18, 2014 8:23 PM
Subject: [NavList] Weems LOP Short Table Method
Hello:
Thanks to a recent post by Greg which got me interested, I've learned to use Weems 1927 LOP book/method. I highly recommend it. It is one of the early short table methods, and it is quite easy. I was lucky to find a 1942/1943 printing of this very thin book (actually mostly Tables A and B) for solving the navigation triangle. The 1928 and later printings cover all latitudes. Only a nautical almanac is needed with the LOP Book .
H.O. 249 became available in the late? 1940s, and this latter method is more intuitive, but the results are exactly the same. I did a recent sight set of data by calculator, H.O. 249, and Weems 1927 (using my 1942 Book), and got exactly the same Hc and Z.. For me, the calculator is the fastest method, and H.O. 249 is also very quick. Weems tables A & B are logarithms (aids to solutions) and not as intuitive, but easy to use. As
stated by Greg, Weems also offers a simple equation for getting Z, and by ignoring his complicated rules for Z and just knowing the quadrant of the celestial body, it is easy to get Zn.
For someone not wanting to purchase volumes two and three of H.O. 249, consider Weems 1927 LOP Book as a second method of solution. Maybe you can find a copy at a reasonable price, as I did.
YES, I do my reductions by hand because I need to "see" the solution unfold. I make enough errors and it is easy to check(erase) results.
Bruce
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