Emergency Celestial Navigation

Increasing reliance on complex electronic navigation systems - nowadays generally available on pleasure yachts - has changed the perspective of emergency navigation. Today, it is more likely that a navigator will suffer failure of electronic devices or the associated power supply and be left with little more than a sextant to navigate with, than that he will be forced to navigate a lifeboat. In the event of failure or destruction of electronic systems, navigational equipment and methods may need to be improvised.

Almanac Data

Only the declination of the Sun can be accurately enough detemined to be usefull. It is a Sine function between the two dates of solstice and with an amplitude of 23.4 degrees. This can be evaluated on a piece of paper and the protractor from the basic navigation plotting tools.

Graphical Method for Sight Reduction

Without appropriate Sight-Reduction Tables and electronic calculator it is still possible to obtain a relative accurate result for the Sight-Reduction calculation with the following graphical method.
I have to credit Marco A. Costa, for leading me to the insight that there is a simple method of graphically multiplying Sine and Cosine values.
The method is demonstrated in the following Worksheet: Worksheet for graphical Sight-Reduction

... more explanation to come ...

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