The Cross staff was created to help European explorers navigate the seas by giving a straightforward measurement of the angular separation of two celestial objects.Although this tool was more accurate on land than at sea.To use a Cross Staff, you adjust the moveable components to a specific date and time.Once set, much of the sky, both visible and invisible , most of they sky is presented on the face of the instrument.

Image of A cross staff

The Cross staff was used to sail and return Back home