I've replaced the fan with a bigger one, this one is bigger than than the heat sink a little bit, so the cooling is much more effective. I'm using a bigger fan in the hope that the Peltier can be driven by the same 12V source instead of using a 6V source. Previously, if I use a 12V source, the fan cannot drive the heat fast enough so the cold side of the Peltier will be overwhelmed, and therefore, I will have to go back to 6V. This is both inconvenient and not using the Peltier to its full potential.
In short, the experiment is very successful. I turned on the Peltier and the fan for over 15 minutes and the cold side is still cold, even with a heat load (which is my body), the heat sink is very hot, even a bit too hot to touch, but it didn't overwhelm the cold side! That's enough. The air driving out from the heat sink is a bit warm.
When I finished the experiment, I turned off the power to the Peltier first and I found that the cold side get warm very rapidly, due to the high temperature from the hot side, but since the fan is still on, it got cooled down too within one or two minutes. The heat sink got cooled down within 10-20 seconds (I didn't measure).
So, finally, I plan to use the whole thing without the moisture insulation box, since the cooling effect is not that strong. Without a load, there's some water droplets on the cold side, but with a load, no water there, or maybe just a trace, so I believe dew is not an important issue here. Even if there's some dew, I believe a simple plastic bad trick, with dessicant would do the job rather than using a full size box which is bulky and troublesome to maintain.
So, now I will need to find a small plastic board, to drill holes for the cable, install the power socket, connect the power to it, make a slot for the Peltier, hold the fan, heat sink and Peltier there, maybe add an adjustable clamp for the attachment of a camera, done.
I believe it will stay on my DBK for most of the time. Cooling is not very useful for the sun since the exposure is short enough, of course, maybe it's useful too? So, a removable mechanism is desirable so that it could be used with my DMK, too.
Another short project for the coming weeks.