Two tasks defined astrogation: determining present location, and planning a safe and reliable means of reaching a destination. The former was performed by those skilled in astrocartography, familiar with star patterns or automata. Astronav charts mapped areas of space and could be used to plot courses through hyperspace. The plotting of a course was generally handled exclusively by astromech droids or navigation computers.
The knowledge of one's whereabouts in space and other celestial objects was vital to navigating hyperspace, as incorrectly calculated jumps meant a ship could collide with a planet, star, or other body.
Behind the scenes
Astrogation is an original sci-fi word which means "star navigation." Since etymologically and historically the part "navi-" refers to terrestrial ships, it has been replaced by the prefix "astro-."