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Latitude by Polaris

The procedure for finding your latitude from the sextant height of Polaris. This unique star sight is especially convenient since no precomputation is required; just set your sextant to your DR-Lat, look north, and Polaris will be in view with the horizon.

The simple sight reduction required is explained with examples in the Nautical Almanac — interestingly, this is the only place in the Nautical Almanac that explains a way to navigate with the data provide in the book, meaning step by step way to get a Lat. (For completeness, there is in Sec 11 on p 282 formula for Lat and Lon based on Hc and Ho of several sights. But then you must get Hc from the NAO tables, and find instructions for the Ho corrections... and then have a great deal of patience as you work trough the complex equations... so our statement about the uniqueness of lat by Polaris in this regard is not far off.)

Once you have found your latitude this way it is plotted on the chart as a line of position and used with other sights to find a fix.

See Polaris, Precomputation, and Polaris Corrections.


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