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Hi all,

Longitude by Sunset or Sunrise was a common discipline
in years gone by; in fact, it frequently appeared on
license examinations given by the US Steamboat
Inspectors.

The candidate was expected to use the Longitude Time
Sight, modified so that the resultant negative
altitude be subtracted from the sum of the Latitude
and Polar Distance, added to the 1/2 Sum, and the
solution otherwise normally completed for Longitude.

The method was suggested for Lifeboat Navigation
during World War II, and otherwise, however, I can
cite no circumstances known to me of it's use.
Otherwise, circumstances do, from time to time exist,
particularly in the North Atlantic, wherein there is
exhibited a reasonably clear horizon in the AM and an
otherwise clouded sky during the remainder of the day,
suggesting the possibility of obtaining at least
an approximate Longitude at Sunrise, if no other means
be available.

There are a number of methods for determining Latitude
without a Sextant, most of which have been discussed,
but none of which seem to approach the potential of
accuracy offered by observations for Longitude at
Sunset and/or Sunrise.

Regards,

Henry


--- frankreed@HistoricalAtlas.net wrote:

>
> Jim writes:
> "In his chapter "Celestial Navigation Without a
> Sextant" he has a worked
> example using the sun as it sets which he claims
> "the LOP produced agreed
> exactly with the distance run since a fix made
> earlier by advancing sun
> lines"."
>
> Sometimes ya get lucky! It might be fun to try this
> ten days in a row and
> see how well it works on average.
>
> And:
> "I haven't tried this type of sight myself but was
> always a little curious
> to try it."
>
> Supposedly, Nathaniel Bowditch himself experimented
> with these sextant-free
> sights on his first ocean voyage in 1795 but
> abandoned them. In his case,
> though, I think he was trying to observe the rising
> and setting of stars.
> Since he had never been to sea before, he apparently
> did not know that this
> was basically impossible. And since they had no
> chronometer, the value of
> these sights was minimal anyway.
>
>  -FER
>
>
>
>
>



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