But this increases focal length, causing telescopes to have to be long and skinny. A solution to the problem of long telescopes. First built by Newton in 1668. Used a parabolic mirror. Catadiopteric telescopes use lenses and mirrors.
Larger telescopes allow observewrs to see fainter objects.
Since mirror or lens is a light collector, a larger mirror or lens collects more light. Mt. Wilson, Cal. Major disadvantage is poor resolving ability. Wavelengths of radio waves are 1000's of times larger than those of visible light. Use arrays of 2 or more to increase resolution.