Airmass

The airmass is an additional parameter which influences the transmission. The ETC allows six different values for the airmass: 1.00; 1.25; 1.50; 1.75; 2.0; 2.5 The Airmass (AM) scales the number of photons from the sky background with

(- 0.000278719 ^. AM ^. AM ^. AM - 0.0653841 ^. AM ^. AM + 1.11979 ^. AM - 0.0552132)