NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Latitude by Spica
From: Bruce Stark
Date: 2004 Jan 13, 12:47 EST
From: Bruce Stark
Date: 2004 Jan 13, 12:47 EST
Kieran, I've never sailed on a square rigger, but suspected that "full and by" meant something like a close reach, and steering by the wind rather than the compass. That the course is given as "full and by," without stating which tack, gave me the idea they must be wearing around to the other tack at regular intervals, and I wonder if this was a standard procedure on the whaling grounds. Those ships probably were not very weatherly, even when clean bottomed. Full and by may have kept them fairly near a back-and-forth track, moving gradually to windward. You and I approached the AM-PM problem from different directions, but came to the same conclusion. I figured that since it was spring, the sun's right ascension had to be between zero and six hours. Spica was on the meridian, and her RA is about thirteen and a half hours. So the sun was between thirteen and a half and seven and a half hours past the meridian. That bracketed the time between seven-thirty PM and one-thirty AM, no matter what the longitude. That the latitude is logged for 12 PM, rather than noon, is another clue suggesting an AM-PM mix up. Bruce