Diffraction spike
From Wikipedia, the free encyclopedia
Diffraction spikes are lines radiating from bright light sources in reflecting telescope images. They are artifacts due to light diffracting around the four support vanes of the secondary mirror. Refracting telescopes and their photographic images do not have the same problem. Although diffraction spikes can obscure parts of a photograph and are undesired in professional contexts, some amateur astronomers like the visual effect they give to bright stars and even modify their refractors to exhibit the same effect.
