angular size

Angular size refers to how large an object appears to us from a specific vantage point, measured as the angle it subtends at our eye. It determines the apparent size of objects in our field of view, regardless of their actual size or distance. For example, the Moon and the Sun appear roughly the same size in our sky because their angles (angular sizes) are similar, even though their actual sizes and distances differ greatly. Angular size helps astronomers understand the apparent dimensions of celestial objects, allowing calculations of their true sizes and distances based on how large they seem to us.