Atmospheric distortion looking down is not as severe as it is looking up. This is because the distortion subtends much greater angles looking up than looking do

Atmospheric distortion looking down is not as severe as it is looking up. This is because the distortion subtends much greater angles looking up than looking down, since the distortion is close to the observer. Looking down, it’s also true that, at least in daytime, exposures are very short as well by virtue of the earth being very bright.