## SKYDIP effects

Currently, (the outside temperature) is used instead of in Eq. 8. The effect of this assumption is intricate, because it is used also in the SKYDIP in which and are both determined. If the atmospheric opacities are low, the sky brightness is a linear function of the number of airmass, and thus

(32)
In this case is underestimated, because is usually lower than . An increase in will compensate the lower value of the forward efficiency. If the opacities are sufficiently high, the linearity is no longer preserved, and the fit will be bad. However, for 20 K difference between and , the effect on is only 0.01 for around 0.90.