The Nocturnal, an Antique Navigational Tool

Similar to an astrolabe or a sundial clock, this nocturnal navigational tool, recovered from the wreck of the La Belle in 1996, was one of the few ever found on a shipwreck.

Imagine navigating the open seas in the 17th century. As you sail through the vast open water, how would you determine the time without access to today’s technology?

In 1996, near the bottom of the La Belle’s hull, Archaeologists recovered a wooden instrument from a mass of concreted material next to a brass cannon. The instrument incorporates a combination nocturnal and planisphere. The nocturnal functioned primarily as a time-keeping device used at night. The nocturnal consists of four sections: the base panel with handle and scales, the dial, the central hole, and the long index arm. The nocturnal was designed with the 21st of April at the top, typical of Nocturnals designed to read Ursa Major.

The navigator would hold the nocturnal by the handle in front of himself. He would look through the central hole to see Polaris. He would turn the long arm until it aligned with two stars, either Dubhe and Merak (in Ursa Major) or Kochab and Pherkad (in Ursa Minor). These stars are called “pointers” or “guards” because they roughly point toward Polaris. Once the long arm was in place, the navigator could then read the time from the central dial as through the arm was the hand of a clock.

The instrument could potentially be used to give a rough idea of longitude. Before the invention of the marine chronometer (click here for our previous post on the Harrison Clock), the longitude was calculated using extensive mathematical algorithms.

You can view the La Belle Nocturnal Navigational Tool in the main gallery of our museum.

Today, The Texas Maritime Museum has several artifacts from various ship wrecks on display in the main gallery.

This particular artifact is the Property of France, from the collection of the Musée National de la Marine, on loan from the Texas Historical Commission