Navigating by electronic devices using GPS (Global Positioning System) is usually accurate and convenient. But what happens if/when the electronic system fails? Before our 13,000-mile trip through the South Pacific, Bruce taught himself celestial navigation, finding our position by the sun and stars using a sextant. It was our primary source of navigation aboard our Bristol-40, Impunity..
Using celestial navigation during the daytime, the sun normally would be our only source of position information, and a sun shot would give a line of position. Bruce knew we were somewhere on that line, which he would draw on the chart.
During morning and evening twilight when Bruce could make out both the horizon and some stars, he could get multiple lines of position, one from each star, and where these lines intersected was our position. When getting a line of position from a star or the sun, Bruce would label the chart with “sun” or the name of the star, such as “Vega.”
Bouncing around on a small boat at sea while taking visual observations using a sextant is not entirely precise, but with care each line of position would be accurate, hopefully within a half mile or less. When many miles from land, that is close enough.
Note: The above was aken in part from my memoir, Sailing with Impunity: Adventure in the South Pacific.