The Challenge: Build accurate clocks
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Another solution is the equinoctial, or equatorial,
sundial. The hour marks are drawn on a circular dial which is not flat
on the floor but at an angle to the ground. This angle varies depending
on where you are in the world but always results in the dial being parallel
to the equator. The gnomon points at the North star, which means that
it is at right angles to the dial.
type of sundial is very easy to set up. Once the gnomon is pointed at
the North star and the dial is constructed at right angles to the gnomon,
the sundial is set up in the right direction and elevation to give us
equal gaps between the hour marks. The shadow falls on the lowest point
of the dial at noon and will be a quarter of a turn counter-clockwise from
the bottom at 6am and a quarter turn clockwise from the bottom at 6pm.
We decided to make a big equinoctial sundial, because the bigger it
is, the more accurate it will be. On top of that, the only suitable
metal rings knocking around on the island were very big! Of course,
experts will know that there are still small inaccuracies in measurement.
Local Apparent Time is usually slightly different from Mean
Solar Time because of the path that the earth uses to orbit the
sun. These inaccuracies can be corrected by using the Equation of Time.
A chiming clock