A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Position-Finding
From: Fred Hebard
Date: 2003 Mar 20, 09:33 -0500
There is a link to a riveting, first-hand account of undersea cable repair in the late 1800s at http://groups.yahoo.com/group/Sextants/message/877. At the end of the link is a detailed description of using sun sights through an artificial horizon on land to synchronize the chronometers. The author mentions using a sextant stand, reading the sextant to the second, and the chronometer to the tenth of a second. I wonder what a sextant stand would look like, specifically the part that cradles the instrument; ie, how does one attach the sextant to the tripod. I also wonder what sort of sextant would allow one to read to the nearest second. Regarding the method itself, it would seem to me that one would have to know one's longitude in order to solve for time. The author mentions working "Observations for Time" on each of 20 or 30 observations to arrive at synchronization to the nearest tenth of a second for the chronometers. These guys also seem to be working sights to the nearest tenth or fifth of a minute of arc, although I infer this from the story rather than reading it directly. I would imagine such accuracy would be very helpful in finding cable 20,000 leagues under the sea.