Ken Dunn Wrote:
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> First as Mark points out, they were primarily > determined by celestial navigation at some point. However, celestial navigation wasn’t as simple as looking at a GPS device and writing down the numbers. It was a rather complicated procedure that involved taking sightings with a sextant then based on the time of day where you were, the angles involved, at least one set of tables, and some math (and perhaps other things I am not aware of) you could come up with a latitude & longitude. However if it was a star sighting you had better be using the right star….

The correct procedure was to have at least two men take the sightings at the same time and compare notes before proceeding but frequently that wasn’t possible under wartime conditions. Getting this right on the rocking and rolling open bridge on a U-boat at sea wasn’t all that simple nor was it that simple on the bridge of a ship. The weather had something to do with it too.
> However, this was the best technology had to offer at the time.

Hi,

there`s still more to be said ...

For obtaining a position in astronomical navigation with a sextant, you need a recognizable horizon. By obtaining the vertical angle between horizon and the celestial objects (sun, moon or star) you get the numerical data to find your position. The best time for that is dawn and dusk.
BUT the submarines normally didn`t have the opportunity to surface at that time. For obtaining a position at night - when surfacing was less dangerous, at least before the introduction of radar in aircraft - you did need an "artificial horizon"
The solution was the "bubble sextant", see [hydrography.pro]

greetings, Urs