NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: 7 ways to determine longitude
From: Frank Reed CT
Date: 2003 Dec 24, 16:12 EST
From: Frank Reed CT
Date: 2003 Dec 24, 16:12 EST
Dan wrote:
"I have just started to read an old book called "Spherical and Nautical
Astronomy", a two volume set by William Chauvenet who was a professor
at Washington University in St. Louis. My copy was printed in 1903 but
it appears that it is just a reprint of an 1863 edition."
Yes, that's the "Chauvenet" that you may have seen in a couple of subject lines on the list. It's a classic.
"Chapter 7 is "Finding Longitude by Astronomical Observation" where it
lists seven different methods, which are:
1st method - by portable chronometers
2nd method - by signals
3rd method - by the electric telegraph
4th method - by moon culminations
5th method - by azimuths of the moon, or transits of the moon
and a star over the same vertical circle
6th method - by altitudes of the moon
7th method - by lunar distances"
One little thing to keep in mind is that Chauvenet was an astronomer who was writing for other astronomers. Most of the methods were meant to be used by astronomers at fixed positions on land. The only method significant for ocean navigation is "by lunar distances". His method was probably only used rarely at sea because it came along so late and perhaps because so many other methods were already in place. His analysis of the Earth's oblateness (polar flattening) is clever, and his approach can be applied to other methods of clearing lunars without much modification.
Frank E. Reed
[X] Mystic, Connecticut
[ ] Chicago, Illinois
"I have just started to read an old book called "Spherical and Nautical
Astronomy", a two volume set by William Chauvenet who was a professor
at Washington University in St. Louis. My copy was printed in 1903 but
it appears that it is just a reprint of an 1863 edition."
Yes, that's the "Chauvenet" that you may have seen in a couple of subject lines on the list. It's a classic.
"Chapter 7 is "Finding Longitude by Astronomical Observation" where it
lists seven different methods, which are:
1st method - by portable chronometers
2nd method - by signals
3rd method - by the electric telegraph
4th method - by moon culminations
5th method - by azimuths of the moon, or transits of the moon
and a star over the same vertical circle
6th method - by altitudes of the moon
7th method - by lunar distances"
One little thing to keep in mind is that Chauvenet was an astronomer who was writing for other astronomers. Most of the methods were meant to be used by astronomers at fixed positions on land. The only method significant for ocean navigation is "by lunar distances". His method was probably only used rarely at sea because it came along so late and perhaps because so many other methods were already in place. His analysis of the Earth's oblateness (polar flattening) is clever, and his approach can be applied to other methods of clearing lunars without much modification.
Frank E. Reed
[X] Mystic, Connecticut
[ ] Chicago, Illinois
