DIY Sextant

James over at Hell In A Handbasket posted a great link to a page on how to build your own sextant with parts you may have around the house. I'll add it to the list of things I'd like to do when I get more time.

I have no earthly idea how one actally uses a sextant. I know that the Brits were using them in World War II for land navigation in the desert. David Brin used them as a plot device once in a novel whose name escapes me. (Hell, I'm not entirely sure it was David Brin.) I'm vaguely aware that one uses tables, a clock, and celestial objects to figure out where you are. Frankly, a good compass strikes me as a much simpler procedure if you can get away with it.

Having been out in the middle of the desert in Saudi Arabia, I know navigation can be a bit tricky without landmarks. We had maps that were, for the most part, useless. DMA used pink to indicate when they felt the terrain would shift. When you pull out a map and the whole damn thing is pink, you know you're just screwed. This was back in the days before GPS receivers were available everywhere. We had two for the entire troop. I spent most of my time over there with no actual knowledge as to where we actually were. We outran our maps pretty fast once we got going. A sextant would have come in pretty handy, as would the knowledge of how to convert longitude and latitude to grid coordinates.

Oh, well. I don't expect to be anywhere like that ever again. If I am, I'll just have to hope I have a GPS and lots of batteries. Or my home-made sextant and an ephemerides table...


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