ADVERTISEMENT. 
To the practical navigator, the ready determination of the Sun’s true bearing 
or azimuth has always been deemed of great importance, but more especially 
will the advantage of tabular results be appreciated at the present time, when 
however carefully the compasses of an iron or steel-built ship may be corrected, 
so much depends upon frequent observations of the deviation under the 
varying conditions of a ship at sea. 
In the Azimuth Tables by Thomas Lynn, Commander in the late East 
India Company’s Service, which were published in 1829, the Sun’s altitude 
is the chief element involved for finding the azimuth, the time not being 
employed. 
In the following Azimuth Tables (for the zones between the parallels of 30 Q 
and 60° in both hemispheres),* the time is the chief element employed, the 
azimuths being computed from the well-known problem in spherical trigono 
metry, viz.—two sides (co-lat. and pol. dist.) and included angle (hour angle, 
which for the Sun is the apparent time from noon,) being given, to find the 
angle at the zenith, which is the azimuth. 
The apparent time at ship is readily determined by altitudes of the 
heavenly bodies, or it may be found, with sufficient accuracy for this purpose, 
by computing it from Greenwich mean time, the equation of time, and the 
longitude in time. 
Results exhibited in a tabulated form have certain advantages. In these 
tables, for example, the value of an error in either of the three elements used 
in the computation is seen at once, and hence the most desirable time for 
making the observations, so that an error in either the apparent time, latitude, 
or declination shall produce the least error in the true bearing. 
As greater dependence can be placed on the result when the magnetic 
bearing of the Sun or other heavenly body is observed at a low altitude, the 
azimuths in the following tables are not given when the altitude exceeds 
60 degrees. 
Supplementary Tables are appended of the Sun’s Declination and the 
Equation of Time ; the latter table will be found convenient to vessels in 
port, provided with local time for reducing mean to apparent time. 
The time and bearing given in the tables of the Sun’s rising and setting 
refer to the Sun’s centre, but as, from the effect of refraction, the Sun’s centre 
at rising or setting is elevated about 33' above the horizon, it will be necessary 
to determine its bearing when the lower limb of the Sun is nearly 16', or its 
semi-diameter above the horizon. 
In determining—by these Azimuth Tables—the deviation caused by the iron 
in the ship, it is obvious that the difference between the Sun’s true bearing 
or azimuth and the Sun’s bearing by compass as observed at the same time 
*In continuation of these Azimuth Tables those for the zone 30° N. to 30° S., which have been 
computed by the late Captain J. E. Davis, R.N., F.R.Gr S., and P. L. H. Davis, F.R.A.S. are 
added to the present Edition. 
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