The main reasons to choose fan over TEC:
1: Majority of noise reduction occurs in the first few degrees see attached graph
Hypercam CMOS Dark Noise and Cooling Temperature Chart
2: Unlike cameras without a fan such as DLSR or non-fan CMOS the temperature tends to stay more constant and stable with the air circulation so the calibration is more accurate – every subframe has it’s temperature recorded
3: No external power is required, the camera is powered by the USB port
4: More cost effective than a TEC CMOS or DSLR
5: Lighter and smaller than TEC cameras
Disadvantages of fan cooled over TEC:
1: You can’t select the exact darkframe temperature for calibration and need to take your darks after the session or before it whilst the ambient temperature is similar to your imaging run (within a few C still works OK for calibration though).
2: You can’t control the degree of cooling precisely – this depends on the ambient temperature. The temperature is however displayed and recorded per frame for calibration purposes and many will create a “dark library” of master-darks at various temperatures to use as needed.
Of course budget and practicality considerations aside, there are plenty of very impressive images taken with fan cooled cameras and they are a step up from non-fan cooled cameras.
Check out the Altair Facebook group for examples.