ANSWER:
The instrument which is used by navigators to calculate the "position of the sun and the star" is Astrolabe.
EXPLANATION:
- Astrolabe is named after the Greek word Astron and lambanien. It’s a two-dimensional model which is in inscribed brass discs used for observational and reckoning time purposes.
- With the help of astrolabe, an astronomer can make accurate measurements.
- Planispheric astrolabe is used to calculate the position of the sun and the stars with the help of both horizon and meridian. Thus, it can be considered as an analog computer.
