Even day sailors who rarely lose sight of land could enjoy learning the skill to fix a position if your chart plotter or electrical system decide to join the choir eternal.
And for those sailors who find yourself in blue water with terra firma beyond the horizon, making a celestial observation of the sun at meridian passage (aka ‘mer pass’) is one of the simplest, yet most useful navigation tools to possess.
With just a sextant, a chronometer and a nautical almanac, you can get a very good estimate of latitude and a fairly good estimate of longitude. Taking a night-time observation of Polaris (the North Star) is another straightforward way to determine latitude alone.
This simplified primer and accompanying pro forma are designed for locations with latitude >23.5°N and westerly longitude. While this mer pass solar observation is both simple and useful, the big limitation is that the sun must be visible at solar noon.
Names explained
It’s difficult to sail effectively until you know the difference between a sheet and a halyard; likewise, celestial navigation is hard to grasp until you have an
understanding of the basic nomenclature:
■ Angles are measured using degrees, minutes and tenths of a minute (eg
