The Bull's Eye Asterism

The Bull's Eye Asterism is an optical effect seen when observing a star through a telescope with a central cross or diffraction pattern. It appears as a bright, circular halo surrounding the star, resembling a bull’s eye target. This phenomenon results from diffraction and internal reflections within the telescope's optics, particularly when viewing bright stars. It creates a captivating, concentric glow around the star, enhancing its visual appeal but can sometimes make precise astrophotography or star measurements trickier. Understanding this effect helps astronomers interpret images more accurately and appreciate the intricate interactions between light and optical systems.