Boys start to get acne at the age of approximately 12 years, with a range of 9 to 15 years old. As most girls will attest, boys on average mature later than girls. Early on in the onset of teen acne, the main lesions are blackheads and whiteheads.
The angular size (angular diameter, apparent size) of an object as seen from a given point is the visual diameter of the object measured as an angle. The visual diameter is the diameter of the perspective projection of the object on a plane through its center that is perpendicular to the viewing direction.
An arcminute can also be divided into 60 arcseconds (abbreviated 60 arcsec or 60). The angle covered by the diameter of the full moon is about 31 arcmin or 1/2Â°, so astronomers would say the Moon's angular diameter is 31 arcmin, or the Moon subtends an angle of 31 arcmin. If you extend your hand to arm's length, you can use your fingers to estimate angular distances and sizes in the sky.