Pickering (2002) developed X = 1 sin ⁡ ( h + 244 / ( 165 + 47 h 1.1 ) ) , {\displaystyle X={\frac {1}{\sin(h+{244}/(165+47h^{1.1}))}}\,,} where h {\displaystyle h} is apparent altitude ( 90 ∘ − z ) {\displaystyle (90^{\circ }-z)} in degrees.
Pickering (2002)發展的： X = 1 sin ⁡ ( h + 244 / ( 165 + 47 h 1.1 ) ) , {\displaystyle X={\frac {1}{\sin(h+{244}/(165+47h^{1.1}))}}\,,} 此處 h {\displaystyle h} 是視高度 ( 90 ∘ − z ) {\displaystyle (90^{\circ }-z)} ，以角度為單位。