Angular size is a Greek geometric concept for astronomical measurement and it is also the basis for modern astronomy. The angular size can be measured in units of radians, units of degrees, arc minutes (1degree= 60 arc minutes) and arc seconds (one second= 60 arc seconds).
Angular size has two measurements, the angular distance and the angular diameter. Taking measurements of the angular size of the moon is also determining the angular distance of the two objects. One basic example of using the angular distance is the angle between your arms. Each fingers from both sides of the arms pointing at an object.
Angular size is simply defined as the distance in between the two ends of an object. It is the same as measuring your height from the top of your head down to your feet. Angular diameter has a measurement of 206265 X (Actual diameter/Distance). Angular diameter is an angular size of an actual size and the distance of the object.
How to determine the actual size of the moon will be determined in using the measurements in angular sizes in seconds of arc. Some bigger objects in the solar system would appear to be small because of its distance. So it is important to determine the correct measurement for angular sizes both in kilometers, miles and etc.