NavList:

I’ve been doing some research on P.V.H. Weems, and I recently discovered his lesser known short method: “The Secant Time Sight.”  There is a copy freely available via HathiTrust if anyone is interested (link below). 

A few things that I found interesting about this method:

1. It was published in 1944, and the preface states: “…about 25% of Merchant Marine navigators will cling to the time sight method. This preference is due to tradition, aversion to plotting, influence of examiners, and to other causes.”
2. The tables, which are only 7 pages long, are the same as Table B from Weems’ “Line of Position” book, and they are simply log secant / cosecant values tabulated for every minute of arc up to 90 degrees. 
3. Perhaps the most valuable part of the book is the workform suggested by Weems for the time sight calculation, which is attached here for those who are interested.
4. Since the work is accomplished with secants and cosecants, one could easily use this workform with Ageton or the “Line of Position” book (or any other related tables). 
5. Rather than doing the math twice to obtain a line of position (which would require more than one cup of coffee for me), Weems advocates calculating longitude once and then determining azimuth (via the Rust diagram) for drawing the LOP thru the calculated longitude and the assumed latitude (perpendicular to the azimuth). 

I’ve enjoyed working thru a few problems with this method, and I’m finding the errors to be typically less than 2nm from my actual longitude.  If you’re a fan of short methods and time sights (maybe I’m the only one!), you might find this interesting. 

-jp

https://babel.hathitrust.org/cgi/pt?id=mdp.39015018437973&seq=1

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