what astronomer was reasonable for the idea the earth was the center of the universe?

Answer 1

Originally, Ptolemy, echoed by Plato. The medieval church thought that Plato was the last word on anything not in the bible.

Answer 2

There was no one astronomer or individual responsible for the idea. It was a case of common sense observation being accepted, and turning out to be wrong. From the point of view of a man on the surface the Earth does not seem to be moving, and everything in the sky appears to be going around it. It became accepted because no-one could prove it wrong. Even today explaining how we know the Earth is not the centre takes time, detailing the motion of the planets in the sky, the relative sizes of the Earth and the Sun, and the observation of stellar parallax. For someone who has not familiarised themselves with these things, it seems perfectly reasonable that Earth is static and immobile at the centre of everything.

Answer 3

it wasn't an astronomer, it was a religious doctrine. hence Galileo's problems when he had the audacity to suggest otherwise.