What all this tells me Steve is to take dummy images to get your sensor up to temperature and then take your lights and darks. If your ambient changes your sensor temperature will change by the amount ambient changes albeit slowly. In the case of my Canon 5DH it is 17C above ambient once equilibrium has been reached. I am afraid that an uncooled CCD heats up even more as they consume more energy.
The aim of the post was to show how sensor temperature had no real correlation with ambient as it depended on the exposure history. My carefully controlled experiment just gave me an insight into what was really happening. I do not think it can be used to control sensor temperature as the hysteresis between ambient and sensor temperature is too great.
Here is a much better graph
http://www.iceinspace.com.au/forum/s...ad.php?t=43805
Bert