thanks Jeff. I've ordered a USB data logger. Great suggestion! I'm in Sydney Australia ... high humidity and high temperatures.

The Pelican case I use has one of those Gortex valves ... do you think that more than one would be more helpful?

My lens is a good 1cm behind the housing lens, but I have a polarising filter on my camera ... (2 sheets of glass already close together) ... might try taking that off.

Etienne