[41south]

Just to add this,

http://www.clearskycalculator.com

Is a very useful tool to check the solar radiation output from any solar sensor. On a clear, pollution free day (which I am sure you get plenty of in Picton) your sensor should read no more than the figure the calculator calculates on any given day of the year, latitude etc. and an offset applied to the readout if it does.

Yes that's my "go-to" calculator for all my testing with these different devices. I suspect that both the ones mentioned saturate quickly with full sun. The analogue one from Adafruit I'm testing also outputs a logarithmic curve, so the math is even more interesting but well supported (for Lux output) in the code examples available. I found 2 sources that use a factor of Lux * 0.0079 to convert to w/m2, but I agree with you that it is a little more complicated than that. However it may be ok for hobby use

All good fun experimenting though.

Colin