[glend (Glen)]

I was imaging last night after moon set, so from 1:30am onward. At that time it was still 23C ambient and 77% humidity (typical Aussie summer night on the coast). The cold finger system on my 450D pulled the sensor down from the internal temp of 24C to 0C within 5 minutes of startup and held it there for the next two hours while running 5 minute subs, with only ten second intervals between subs. The point here is that I don't know of another current technical solution that can produce such efficient, reliable, controllable, cooling of the sensor for a reasonable investment (and I have looked at this technology for the past couple of years). Alternative solutions have been promoted and trialed over the past few years: cooler boxes, gas change of state systems, external camera body cooling, etc. IMHO these designs are all flawed in that they do not address the main criteria required for astro dslr cooling: the ability to efficiently cool the sensor to a setpoint that is consistent with optimal sensor noise performance. The main issue that cold finger implementations bring is condensation, but that is an issue for any of the alternatives as well. Dessicants, body sealing (or bagging), dry air or gas purging, all can be made to work. It is worth noting that the professional Astro CCD camera builders still rely on sealed sensor chambers and direct cold finger cooling.