In Resnick's book on introduction to special relativity he mentions two effects that contradict the ether drag hypothesis. Fizeau convection coefficient and stellar aberration. He says that if ether was to be moving along with the earth then the light coming from a star directly 'overhead' wouldn't appear to move or in other words we would not have to correct the telescope angle due to earth's motion around the sun. In his words:
ether is not dragged around with the earth. If it were, the ether would be at rest with respect to the earth, the telescope would not have to be tilted and there would be no aberration at all.
This wiki animation shows what he means. What I'm doubtful about is that since the earth is changing its position with respect to the sun all stars should appear to move in the night sky regardless of the presence of an ether medium. So how does it make sense to argue using this point? Does stellar aberration tell us that no star should be visible directly overhead due to earth's constant motion? Does the star appear to move during the time you're seeing it through the telescope?
Note: I have studied Michelson-Morley experiment and am quite convinced that ether is an unnecessary hypothesis. I'm only seeking a clarification on the phenomenon of stellar aberration.