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Mike it does take some time stacking each exposure set and then getting each to match in size and area with Registar. If everything is done correctly in EasyHDR then it is simply amatter of adjusting levels of the final LDR in PS.
It is well worth it as I can get any amount of dynamic range in the final LDR image up to about 20+ bits or stops. This is more important with wide fields because of the variation in intensity of the objects. At 200 ISO and a seven second exposure the brighter stars are nearly saturated. As you can see all the stars have colour and the dim nebs come up noise free.
Ingo the fans can be speed controlled and once the fridge is down to 20+c below ambient I turn them down from flat out to a whisper. These fans are high quality ball bearing and well balanced so vibration is not a problem. Even the TAL200K with a focal length of 1800mm shows no image deterioration due to vibration.
The heat sinks are CPU heatpipe coolers and the hot side of the Peltier is less than 35C depending on ambient.
I replaced the original peltiers with these from Jaycar.
Temperature Differential (DT) (Th=27 degrees C) : >=68 degrees C
Optimum Input Voltage (Vmax) (Th=27 degrees C): 15V
Optimum Input Current (Imax) (Th=27 degrees C):8A
Maximum Cooling Power (Qmax): 68.09W
I run them at 13.8V and 6A as this seems to be optimum for their current physical installation. If the voltage is increased from 13.8V the fridge temperature goes up. Peltiers pump about half the heat of the energy used to drive them. So I estimate this fridge is pumping about 80+ watts.
With one Peltier running I get 15C drop from ambient and with two 25C drop from ambient with the camera exposing. With the camera at idle or off the fridge temp drops by 2 or 4 degrees respectively.
The real advantage of the fridge is I can get noise free data at 800 ISO and only a tiny amount at 1600 ISO at about -5C. In winter should be able to get -20C with ease. The longest exposure was 2min at 800ISO. Four minutes at 800 ISO was too saturated to use.
Below are images from just the 2min at 800ISO data. The nebs look fine but the stars are washed out. The background is also lighter due to skyglow.
Bert
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