angular width; angle width
Technical term used in physics and optics to describe the angular extent of an object or beam.
The angular width of this lens is narrow, so it cannot observe a wide area at once.
Specialized equipment is needed to measure the angular width of celestial bodies.
幅 means 'width' in a linear sense, whereas 角度幅 is the angular equivalent.
Compound of 角度 (angle) and 幅 (width), literally 'angle width'. A straightforward technical term.