Astrolode

An astrolode is a navigational and astronomical instrument used to calculate current latitude and longitude by taking bearings on the Fixed Stars, which hang in fixed points over the equator.

It combines an astrolabe (used to calculate the height of a star) and a lodestone, or magnetic compass. Longitude can be calculated from the elevation of the star: the lower the angle, the further north you are. Latitude is calculated from the angle between the nearest fixed star, and magnetic north, as shown by the lodestone. When a ship is due north or south of a fixed star (ie the star has a bearing of 0 or 180 degrees), they are on the meridian of that star. The angle changes the further east or west a ship goes.

Two fixed stars can be used to calculate a very accurate location, assuming the navigator has the right tools, charts and mathematical and navigational skill. Using two stars is ideal, but close to the Yending meridian the two neighbouring stars only appear on the horizon.