NavList:

Another historic table for finding azimuths is found in H.O. No. 171 "Line of
Position Tables (for working sight of heavenly body for line of position by
the cosine-haversine formula, Marcq Saint Hilaire Method)"  US Navy Bureau of
Navigation 1915. Table V the Finding of the Azimuths, page attached.

The table is entered with the dec (across the column headings) and hour
angle (in hr and min, down the column) to find a tabulated number. Then the
tabulated number is located again in the dec column whose heading is closest
to Hc and the Az is read off in the hour angle column and its direction
determined by the usual rules.

The rest of the tables in HO 171 are altitude corrections and log sines, log
cosines, and log and nat haversines.

John Cole

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From: Chuck Taylor <cft98208@yahoo.com>
Reply-To: <NavList@fer3.com>
Date: Tue, 9 Oct 2007 21:12:56 -0700 (PDT)
To: <NavList@fer3.com>
Subject: [NavList 3400] Re: Burdwood's Tables

Here's a page from Burdwood's Tables. The latitude limit is 64 degs in the second edition. Commander John Burdwood RN was was in the Admiralty Hydrographic Department.  The second edition 1940 was revised by Percy Davis FRAS of HM Nautical Almanac Office.

I have a pair of azimuth tables

H.O. No. 71  Azimuths of the Sun and Other Celestial Bodies of Declination 0 to 23
                      [Fifteenth Edition] United States Navy Department Hydrographic Office
                      1934
H.O. No. 120 Azimuths of Celestial Bodies Whose declinations range from 24 to 70 degrees
                       for latitudes extending to 70 degrees from the equator
                       [SEVENTH EDITION] United States Navy Department Hydrographic Office
                       1940

What is the relationship between these two sets of tables and Burdwood's Tables? They appear to contain essentially the same data, except that in H.O. No. 71 the azimuths are given in degrees and minutes (vice degrees and tenths) for every 10 minutes of time (vice every 2 minutes of time). Another obvious difference is that Burdwood's tables are British, and these are American.

There is no mention of Burdwood in either of these publications.

Here is an excerpt from the preface of H.O. No. 120:  

     "This work was prepared by the Hydrographic Office in 1902 on account of the value of star observations in determining azimuths, and the growing necessity of frequent observations for position in high-speed ships.

     "Taken together with the solar azimuth tables of the Hydrographic Office, which give the true bearings of the sun and other celestial bodies within ecliptic limits, the present tables supply the navigator with ready means for finding the azimuths of the great majority of bodies appearing in the firmament and for applying, over a vastly increased extent, the other useful objects of azimuth tables, such as finding the true course in great-circle sailing and laying down the Sumner line of position."

Best regards,
Chuck Taylor
  48d N
122d W


 

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