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I had the pleasure of visiting David Burch last September at the Starpath
headquarters in Seattle. David had a sextant very similar to the one
described here by Bill and we took it outside to take a sighting of the
sun. After heading back inside to reduce the sight, we were only about 8
minutes out. A very impressive demonstration on what can be done with such
a simple instrument.

If I were trying to introduce a bunch of 11 year olds to the ideas of
celestial navigation, I think this would be the route I would take.

Geoffrey Kolbe



At 15:46 27/11/2007, you wrote:
>
>
>This may not give the level of precision you're looking for, but it's
>simple and easy for kids to understand:  Make a quadrant out of
>cardboard.  Print the protractor with a laser printer, either directly
>onto light cardboard, or onto paper that you glue to heavier
>cardboard.  Make sure the zero is parallel to one edge of the
>cardboard.  Cut around the arc so you have a quarter-circle, or a
>half-circle, or something in between.  Poke a tiny hole exactly at the
>vertex, and insert a thread.  Tape it in place on the back, and tie a
>weight (I used washers or nuts) so the thread hangs taut just below
>the arc.  Tape a drinking straw along the edge of the cardboard for a
>sight, so it is supported by the edge like this:  O==  To sight stars,
>you look through the straw with one eye, and around it with the other,
>and place the star at the center of the circle.  Rock the quadrant
>until the stationary thread just grazes the cardboard, pinch it in
>place, then read it.  You should be able to read to 15' or better with
>a reasonable-sized scale, though your sights will likely have more
>scatter than that.  For the sun, don't look through the straw --
>instead, watch the quadrant's shadow, and point the straw at the sun
>until its shadow becomes an "O".  Again take care that the quadrant is
>in the vertical plane, and pinch the thread.  (This measures to the
>center of the sun, not to either limb.) You should check each quadrant
>for index error -- assuming your printer is properly adjusted, and the
>thread pivots in the center of the arc, other errors should be
>negligible.  Good luck!
>     -- Bill
>
>On 11/27/07, Isonomia  wrote:
> >
> > I'm camping next summer with a load of 11year old kids and wanted to
> > do some celestrial navigation and plot a position to within
> > 10-20miles.


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