Staring at the sun: MLO calibrations of sunphotometers

We recently did a trip to Mauna Loa in efforts to calibrate our sunphotometers. Here we see the 4STAR tracking the sun along side its predecessor AATS, and the ground based Prede. The Mauna Loa Observatory (MLO) is chosen for this event because of it's high altitude, and remoteness (middle of the Pacific Ocean).