Astronomers rely heavily on telescopes in order to observe the night sky. However, there are certain phenomena that occur, which can make stargazing difficult. The resolution of telescopes can be limited by numerous imperfections in the lenses, and it can also be hindered by the diffraction limit.
Waves, including light waves, can bend around corners whenever it hits an obstacle. As a result, the quality of the image observed under the telescope is compromised. Diffraction limits occur because the telescope lenses are finite and therefore diffract light to cut off some of the light wave.
Telescopes on earth have a much lower resolution than their diffractive limit because light waves travel through turbulent atmospheres. These atmospheric effects combined with the diffraction limit of telescopes can make objects appear distorted. Fortunately, there are certain techniques that one can employ to improve the quality of the images being observed.
The use of inter-ferometry has been a valuable technique to beat the diffraction limit. Here, signals from two telescopes are combined so the interferences they impose on each other are studied to diagnose the original state of a wave. Near-field and far-field techniques are some of the other techniques that can be employed to beat the diffraction limit.