Astronomy - as-t-rA- namA-ya - The instrument to coin a name (of a person). It is still relevant in India to names babies after consulting the stars and horoscope. Astronomy is still significant in marking auspicious days and festivals. The same was true for Persians, Babylonians, Syrians, Greeks, Italians, Mayans, Incans, Peruvians, and so on.
as - Strong root for 'be', 'is', 'are'.
as-t - Weak Present Participle which makes it Action Noun.
as-t-R - Makes it root for Agent Noun. The Singular form is as-t-rA.
namAya - To name, for naming, something to be named.
as-t-rA-namA-ya - An instrument to name.