Notices by InquisitorVendee (inquisitorvendee@poa.st)
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@Tovarish_Pedal @WashedOutGundamPilot @Eiregoat @Rayfield It is an entirely mechanical, yet very accurate time piece that was essential to deep sea navigation prior to GPS.
Having accurate time-keeping is required for running by dead reckoning (we have gone for x time, in y direction, therefore should be in position y) and for accurate calculation of a ship's position by sighting stars.
To take an accurate celestial fix you need an accurate time and a rough idea of your ships position (within a few hundred miles works, but the closer the better).
Effectively you compare what you DO observe in the sky at your true position against what you SHOULD observe in your estimated position at the same time. The difference between observation and reality allows you to calculate your true position.
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If you aren't bothered about whether they are in working condition, nauticalia generally goes for buttons at antique auctions.
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You should. I'll loan you my grandfather's sextant:
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Generally, anything up there that isn't a celestial body isn't going to cause you any problems for celestial nav for a couple of reasons:
1. They move too quickly to get a sextant reading from. You are looking through a small telescope with a very narrow field of view and trying to precisely match it to a reflected horizon. That takes a bit of time.
2. You need to identify your star before shooting it. None of the calculations will give you anything useful if you don't identify the body correctly. Most navigators learn a couple of dozen major stars and their positions within constellations.
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American Practical Navigator by Bowditch is basically the bible.
msi.nga.mil/Publications/APN
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The fact that the IMO now allows ships to sail without paper charts is an absolute joke.
ECDIS is utter wank. I made a decent living training people how to use them, and I still hate it.
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InquisitorVendee
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