Enhaced Cooling Moravian for CCD G3 and G4.
Dark current, the injection of electrons into CCD pixels regardless of whether the sensor is illuminated or not, is the most important source of unwanted signal in CCD photography. Although the dark current is caused by random processes, it is also highly dependent on the sensor temperature. Normally the dark current is halved with a temperature drop every 5 to 7 degrees Celsius, depending on the particular sensor. While the dark current can be largely eliminated by subtracting darks, a random portion of the signal always remains in the image. This is why CCD sensors in cameras intended for low-light imaging (and therefore allowing many minutes of long exposure) are always forcibly cooled.
Thus, the G3 cameras can reach up to 48°C below ambient temperature and the G4 camera can cool the sensor down to 45°C below ambient temperature.
However, these maximum values provide very little room for regulation and it is not recommended to use such a temperature delta for routine observations, as the camera may not be able to maintain the absolute CCD temperature if the ambient temperature rises.
Since thermal runaway cannot be easily controlled, the only way to achieve lower absolute temperatures is to increase the cooling power.
With this optimized cooling system the absolute temperature of the sensor can reach a temperature of less than 5°C compared to standard models (without this additional cooling system). This may not seem like a big difference, but as explained above, the dark current is exponentially dependent on temperature, so the 5°C temperature drop may result in a dark current intensity close to half, depending on the particular sensor.
Enhaced Cooling Moravian for G3 and G4 CCDs.
