I'm studying to become an astronomer.
I am an astronomer.
Carl Sagan was a noted astronomer.
The astronomer studied distant galaxies using a powerful telescope.
Traditionally, an astronomer directly observed the stars, but nowadays some astronomers instead use data automatically generated by properly programmed telescopes or satellites.
The astronomer's observations proved that cephid variable stars would pulsate in a regular cycle
Galieo was the first astronomer to view Jupiter's moons through a telescope and proved the heliocentric model.
The astronomical star looked like it could be a planet because of its enormous size.
Astronomer's are people (scientists) who study celestial bodies. So by profession an astronomer uses a telescope and not a microscope.
A telescope is the instrument an astronomer uses to study matter in space.
A clock
Galileo.
a lot