Apparent Diameter

The apparent diameter of a celestial object is the diameter measured by an observer at a specific distance from the object. The smaller the distance between the observer and object, the greater the apparent diameter. Apparent diameters are often expressed as angular diameters.

The apparent diameter of the object is larger when observed from point A than at point B, which is further from the object.

Study Astronomy Online at Swinburne University
All material is © Swinburne University of Technology except where indicated.