25 Sep 16
Originally posted by twhiteheadMoving the pickup antenna doesn't effect focus because the dish net is circular. That lowers the effective collection area but means you can move the antenna around with no loss of focus. A parabolic dish would have more gain and resolution but you would have very little motion available for the antenna collectors since the parabolic dish focuses on one point. So a circular dish combined with moving antenna partially solves that problem. The left over is the antenna only has about 15 degrees of freedom but that is enough for most studies.
I wonder how it compares to the SKA. The SKA has the advantage of being able to turn the dishes. I believe fixed dish telescopes can achieve some movement by moving the antenna, but I would expect that would affect the focus.