In part two I said I hadn’t done humidity yet. Now I have – it was *fairly* easy to do and I was short of something better to do in the wee hours of the morning.

**Twelve hours:**

**One day:**

I was asked in #bitfolk whether the station did anything other than temperature and I remembered that WSDL gave the dew point so thought I might as well add that too.

The maths required to calculate dew point and the background information is given in the Wikipedia article but for want of an excuse to use the LaTeX plugin for WordPress, the dew point [math]T_d[/math] is given by:

[math]

T_d = frac {a times gamma(T, RH)}{b-gamma(T, RH)}

[/math]

Where [math]gamma(T,RH)[/math] is given by

[math]

gamma(T,RH) = frac {a T} {b+T} + ln (frac{RH}{100})

[/math]

The bottom pair of lines in the temperature graphs in the last post show the dew point.