Alex,
you know your way around Excel! Nice. Need more data points though.
Would be nice to use Celsius throughout. I wanted to data mine the considerable *big* data that comes out of my observatory, and I wish I had a continuous monitoring of the seeing instead of only when the dome is open and a camera is snapping photos. but our newly acquired hobby farm has keep me from the observatory, still inoperative after the move a year ago ( but this weekend I will work it.
Cheers