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Azimuth by Polaris
Azimuth by
Polaris
Polaris (the North Star) is always within about 2° of true north. The
true azimuth of Polaris is tabulated in the Nautical Almanac in the
Polaris Tables for northern latitudes up to 65°.
Gathering Information: The entering arguments for the Polaris Tables
are the LHA of Aries (GHA of Aries plus east longitude or minus west
longitude) and latitude (at intervals of 5°, 10° or 20°). An extract from
the Nautical Almanac Polaris azimuth table, which appears at the foot of
the Polaris Tables, is shown in figure 9-5. As you can see, the
interpolation can be done by visual inspection of the appropriate LHA
and latitude.
The normal use of Polaris for obtaining compass error is when your ship
is in the lower northern latitudes. This allows you to take a bearing on
Polaris using the telescopic alidade. Since the computation and
interpolation of azimuth by Polaris are relatively simple, we will not go
into step-by-step procedures in this text.
Figure 9-5. Extract from the Nautical Almanac Polaris Tables.
9-11
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