For PSE freaks only!

 

The graph shows the intensity of the skylight during two mornings, in arbitrary logarithmic units. The measuring area is six degrees in diameter, slightly due west of zenith.

The red line shows a cloudfree dawn. The first transient increase of the intensity is a white cloud reflecting more light, compared with the clear blue sky. Later the light decreases quite substantial due to the thick thunderclouds, blocking the light from the Sun between 9:30 and 10:30.

 

The black trace shows the PSE of 2003-05-31 @ FGO. It was not without interfering clouds, but there was a good, but short visual contact, at maximun phase (88 % of the solar diameter), with the Sun. Broken cloudcover did persist during the whole event, as can be deduced from the graph.