The instrument
The sextant is a navigational instrument built for one purpose: to measure the angle between a celestial body and the horizon. Its arc spans sixty degrees, one-sixth of a circle, which is where the name comes from.
By the late eighteenth century it was standard equipment on any vessel making long passages. With a sextant, a chronometer, and astronomical tables, a navigator could fix the ship’s position anywhere on the globe.
Sailors learned to use it in moving seas, often before dawn or after dusk. The work demanded patience: the sextant was built for a single moment, and the navigator had to be ready for it.
The meridian passage
Every celestial body traces a daily arc across the sky. Once a day, that arc crosses the observer’s meridian, the imaginary line running from one horizon to the other through the point directly overhead. At that crossing, the body reaches the highest point it will climb.
That moment is the meridian passage. For a navigator it is the easiest and most precise observation there is: follow the body as it climbs, and the instant the angle stops increasing is the moment to read. From that single measurement, with no clock and no complicated calculation, the navigator knows the ship’s latitude.
A single careful observation, taken at the right moment, tells you exactly where you stand.
Why it matters
GPS has made celestial navigation obsolete in any practical sense, but the practice was never just about the technology. It was about knowing exactly where you stand before setting a course for where you want to go.
That is our work: a clear fix on what you own, what you need, where you’re headed, and what’s possible.
That is Meridian Passage.
Start a conversation
Schedule a call