Now then, homeguard thanks for that, however, I'm in the situation of knowing the %humidity and the OAT, but not the dew point. So is there a way of calculating the dew point with only the relative humidity and the temp?
It's easy if I know the dew point, the cloud base formula that is used on my syllabus is
Air Temp (C) - Dew Point (C) *400 = Cloud Base.