The Armillary sundial operates basically the same way as the horizontal sundial does. Armillary sundials keep track of time more accurately than a standard garden sundial. Most Armillary sundials have a fixed gnomon aligned with the Earth's rotational axis, as well as a shadow-receiving surface symmetrical to the axis.

How do you use an armillary sundial?

Place the sundial on the base but do not secure it. Use the compass to locate true north and point the gnomen in that direction. For the greatest accuracy, the gnomon must point to magnetic north, not true north but to get a "ballpark" directional reading, a standard compass reading is fine.

How does an armillary work?

How does an armillary sphere work? Held stationary at the centre is a small brass sphere representing the Earth. About it rotate a set of rings representing the heavens – the celestial sphere – one complete revolution approximating to a day or 24 hours.