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

-2.78719 . 10-4 . AM3 -6.53841 . 10-2 . AM2 +1.11979 . AM - 5.52132 . 10-2 (15)

It is a polynomial fit to observed sky brightnesses from [SKYREF]. For small zenith distances ( < 40o) it is similar to the van-Rhijn's function (formula 17).



Andre Germeroth 2014-07-17