One problem is that radio waves from these far away objects, even though they can get through, are extremely faint.
一个问题是,来自这些遥远物体的无线电波,即使可以到达这里,也会非常微弱。
2
Under those conditions photographers shoot with a fast exposure time and small aperture. That makes it impossible to capture faintobjects in a dark background, such as stars.