Sensor cooling can lead to moisture appearing in the camera, so the D5500a Cooled uses a special anti-dewing system that uses targeted heat to avoid dew drops appearing.
These are often called "dew heaters", and are really quite simple. It's usually nichrome wire (e.g. what you see in a toaster), or sometimes a bunch of resistors. The tiny amount of heat generated by these straps are enough to raise the optical port a degree or two above the dew point.
My QHY8 (a dedicated astro CCD) for example has a poor/old design, where the CCD compartment is not air-tight. This allows humid air to get inside, which can then fog up the optical glass due to the peltier cooling the sensor down.
The fix is a small ring that screws into the port, and raises the temperature just enough to combat dew. You could also wrap a dew heater strap around the part of the optical train at that point for a similar effect.
Dew (and frost) are the astrophotographer's great, persistent enemy and not just on the CCD. You'll also have dew problems on the telescope itself. For example, my newtonian sometimes has dew problems on the secondary mirror, occasionally on the main mirror, and always on my guide scope.
Most people just create some DIY dew heater straps with nichrome wire... it's super simple and effective.
Interesting. So it's a heating element (wire) which serves as a controlled heater to keep the close environment above dew point. If it's controlled, that is. Maybe it works as a dumb heater also?
OTOH, I've never considered somewhat more performant (not to say extreme) cooling of CMOS in order to eliminate noise. I'm surrounded by CMOS and CCDs every day, in film cameras and telecines (both array and linear chips). I knew, and saw, that temperature can influence noise, but apart from staying within 'normal' operating range, I never considered it would eliminate more noise if significantly cooled down. Probably because I knew noise was inherent to the way those things work and not much could be done to eliminate it altogether. Interesting. I'll try to experiment with a bit more extreme cooling on my equipment to see what yield would come out of it. I'm not that concerned about dew, because equipment is in controlled environment (dry and +-2C deg. stable environment), but nice to know.
A major pain point of dew-heaters is if they are too strong, they induce "tube currents". E.g. the heat from the dew-heater causes the air around the heater to start convecting, which causes ripples in the final image. It's not really visible as ripples, but a general blurring of the image. It's essentially recreating astronomical seeing conditions inside the telescope itself, which is obviously not ideal :)
I think some fancier setups will be "active" and regulate themselves based on ambient temperature, but it's a lot more common for people to over-build their heaters and then use a dimmer switch. So you make your dew-heater for the worst winter night you expect, then dim it down for the rest of the year manually.
I'd like to hear more about this.