observator
/ɒbˈzəːvətə/ /əbˈzəːvətə/ /ˈɒbzəveɪtə/noun
A person who makes scientific observations, especially in astronomy; a person in charge of an observatory; = observer. Now historical.
Origin
Early 16th century (in an earlier sense). From Middle French, French observateur a person who observes a law, a person who makes (scientific) observations and its etymon classical Latin observātor a person who watches over something, in post-classical Latin also a person who observes a law or practice (early 3rd cent. in Tertullian) from observāt-, past participial stem of observāre + -or.