Explanation :
Angular diameter of a sphere or a circle shows how large a sphere or a circle appears from a given point. It is the angle between the initial and final positions.
The angular diameter of a given sphere or a circle is given by :

where
is angular displacement
d is actual diameter of object
D is distance to the center of sphere
So, angular displacement is inversely proportional to the distance from the object.
Hence, as we move away from the object the angular diameter of an object gets smaller.