(also ‘uranologist‘; plural: ‘astronomers‘; for the right pronunciation of this word, please click here)
a qualified person who studies and so knows about stars — planets, stars and galaxies, and their movements in the sky (space), scientifically with the aid of a telescope and other modern devices;
(informal) a stargazer,
By the nineteenth century astronomers had developed the technology to objectively measure a star’s brightness. (from yourdictionary.com)
Ancient Chinese astronomers first observed sunspots, the dark sports we see on the sun, about 2,000 years ago. (from englishbee.net)
Astronomers base their observations on facts and use scientific equipment to investigate, whereas astrologers depend on some ancient writings and scriptures for their guess work.