NavList:

A few years back, while browsing in a used book store, I came across Burton's Nautical Tables, High Latitude Edition". I do not know the publish date for the standard portion of the tables, but the appendix, wherein the "ex-meridian and ABC tables are extended" to latitude 82 degrees is dated 1937.

The book was very inexpensive and due to my interest in the high latitudes, I bought it. It has rested on my shelf ever since.

Not only does the ex-meridian table extend latitude to 82 degrees, it also extends the declinations to 75 degrees. This table is for the values of F, and must be worked with the standard components of the exmeridian table in the main tabular reference.

The pupose of the ex meridian table is fairly straight forward. It is provided such that you can determine your latitude should the meridian crossing by your object (typically the sun) be obscured by clouds.

Much less obvious to me are the ABC tables. There is a footnote explaining that the A&B portions were first published in 1846, and that the C portion was invented by Mr. AC. Johnson.

Can someone explain what the purpose(s) are of the ABC Tables? If its any help, A=Cot(HA)Tan(Lat) B=cosec(HA)Tan(dec) and C=Cot(Az)Sec(lat)

If there is any interest, I can scan the 'high latitude' portions and post them on the list.

Regards
Brad
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