Jacob W. answered • 08/22/20

Chemistry, Astronomy Tutor for HS, College Chemistry, Astronomy

Angular width is measured using the following formula:

α=2arctan(D/2r)

where

α - Angular width

D- diameter or size of object, **3.9 inches **

r - the distance to the object from the observer, **30.6 inches**

If we plug everything in, we get:

α = 2 arctan (3.9 inches/(2*30.6 inches))

α = 2 arctan(0.06372549019 inches)

α = 7.2925 deg == 7.293 deg

For physical reference, your pinkie finger held at arms length is about half a degree, or the same size of the full moon.