Historically, first and foremost, Their Eyes. Even when Astronomical data, provided by the World's most advanced telescopes of several different types, is viewed on the monitors of vastly powerful computers, they still use their eyes.
I'm studying to become an astronomer.
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
telescope
Galileo.
a lot
He was not the first astronomer; there were plenty before him going back to the Babylonians at least. Galileo, however, was the first to use a telescope.
Astronomers use a camera. It begins with the letter c.
Carl Sagan was a noted astronomer.
An astronomer was needed to use latitude and longitude to survey the land. Benjamin Banneker, an inventor, mathematician, as well as astronomer, and the son of a freed slave, was asked to hep with this task.
An astronomer