Question

Concave mirrors are used in telescopes but there is a problem with spherical mirrors called spherical aberration.
(1) What is the problem you would see?
(2) why does it happen (what causes it)?
Finally, how do astronomers overcome this problem?

Answer 1

1. The result is that the images of objects as seen in spherical mirrors are often blurry.
2. Spherical aberration is most commonly corrected by use of a mirror with a different shape. Usually, a parabolic mirror is substituted for a spherical mirror.

Answer 2

oops number 2 is for the finally bit.
The correct answer to number 2 would be: Rays that strike the outer edges of the mirror fail to focus in the same precise location as light rays that strike the inner portions of the mirror. While light rays originating at the same location on an object reflect off the mirror and focus to a point, any light rays striking the edges of the mirror fail to focus at that same point.