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Just to nitpick, method 1, and, later, method 3 (substituting radio for
telegraph), also are used at sea.

Merry Christmas Everyone!

Fred Hebard

On Dec 24, 2003, at 4:12 PM, Frank Reed wrote:

> 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

   

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