relative optical air mass
quotient of the optical thickness of the atmosphere at angle
Note 1 to entry: See also "optical thickness".
Note 2 to entry: Several equations are available to express this concept. Usually the Kasten–Young formula is used:
Note 3 to entry: When the curvature of the atmosphere and atmospheric refraction are neglected:
Note 4 to entry: The relative optical air mass has unit one.
Note 5 to entry: This entry was numbered 845-09-88 in IEC 60050-845:1987.
Note 6 to entry: This entry was numbered 17-1082 in CIE S 017:2011.