Astrocompass

With knowledge of the current time and geographical position in the form of latitude and longitude, the astrocompass is sighted on any astronomical object with a know position to give an extremely accurate reading determining the direction of "true north"

In use the base plate is leveled with the horizon, then pointed roughly to the north. The equatorial drum is then tilted in relation to the base according to the local latitude. The sights are then set using the local hour angle and the declination of the astronomical body being used, based on astronomical tables such as the "Nautical Almanac".

Once all the settings have been made, the astrocompass is simply turned until the astronomical body is visible in the sights. It will then be precisely aligned to the points of the compass.

This astrocompass was loaned to BLMA from the Collection of Alex Brincko: Saunderstown, RI.