Archive for September 19, 2016

09/19/2016 – Ephemeris – How did the pirates of long ago navigate?

September 19, 2016 Comments off

Aye matey, Barnacle Bob here with Ephemeris for Talk Like a Pirate Day, Monday, September 19th.  The Sun will rise at 7:26.  It’ll be up for 12 hours and 17 minutes, setting at 7:44.  The Moon, 3 days past full, will rise at 9:47 this evening.

We tend to romanticize things of the past like the Pirates of the 16th, 17th and 18th century, not so much the Somali pirates of today.  The problems of getting around and finding your way around were difficult in the seas and oceans before the use of the Harrison Chronometer made the precise determination of longitude possible in the late 18th century.  It did require an almanac of star and planet positions plus the chronometer must be set to some time standard of a particular place of known longitude.  Among the Islands of the Caribbean I imagine, though don’t know for certain, that one could dead recon between the islands and crudely navigate that way.  Latitude determination was easy using the Sun.

Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.


Harrison's H1 Chronometer

John Harrison’s (1693-1776) First attempt at a chronometer (1735), which he called H1. Credit:

Harrison's H4 Chronometer

John Harrison’s (1693-1776) fourth attempt at a chronometer (1759), which he called H4. It passed its sea trials. It’s not much bigger than a pocket watch.  Credit: