electric circuit for the solarpanel

Hello everybody,
after our VERY NICE meeting in Badia, we had to solve the problem of measuring the power produced by the solar panel (which can maximal be 20 W). Its tension can rise until 20 V and our datalogger Xplorer GLX cannot measure beyond 10V.
Marie finally bought two resistances (10 Ohms, 25 Watts) that we put in series like this :

This way, V stays always under 10V and the currentintensity stays under 1 A, so our GLX stay happy !!!
And we get P by mulitplying 2 x volts x amperes.
If you want to see the result ... http://www.youtube.com/watch?v=0M65fpljiXk
à bientôt,

Emilie