Hi schmaks,
The sensor used in the 183 is the IMX183, and has in-sensor dark current suppresion like every recent Sony sensor.
It has been tested extensively in this page, most of which is in french.
http://www.astrosurf.com/buil/asi183mm/The version tested was mono-cooled, but the mono version is the same as the colour version except with a bayer matrix in front. According to a known rule of thumb, dark current doubles every 7-8 degrees. Taking this rule of thumb, if they measure 0.0028 electrons/second at -10 degrees Celsius, when the sensor operates at 35 degrees the dark current will be 0.1792 electrons per second or about 1000 electrons per pixel for one hour integration time. With the gain set to unity (about 100) and a quantum efficiency of 60%, it takes about 1 photon every 2 seconds to dwarf that signal. Needless to say unless you live in the middle of the Sahara desert, your skyglow is at least 40 photons per second.
This guy in Cloudy Nights has actually
measured how the sensor performs and it does significantly better than the rule of thumb, dark current doubling every 10 degrees. This means at 35 degrees you are looking at 0.12 electrons per second and in the more realistic 25 degrees you are looking at 0.06 electrons per second which actually puts many a cooled CCD sensor to shame.
Incidentally the fact that the sensor is so indifferent to temperature means if your subs are < 10 minutes you are basically okay taking darks 3 to 4 degrees around your operating temperature in order to get rid of the amp glow which *is* a known problem with every ZWO camera in the < $1500 price range.
So no, I don't think you
need the cooled version unless you are aiming for exceptionally faint targets and/or narrowband. Not that it won't perform better than uncooled, it is just that you can probably spend the extra $300 in something else that will give you more value for the money. Whether the 183 (cooled or uncooled) is a good camera for you based on its other characteristics, I cannot tell. Also I cannot tell if it outperforms your DSLR. As far as I am concerned, I very much wish there was an astrocam which would combine the small size and ease of use of my ASI178MC/MM with the excellent image quality of my Nikon D7500
FWIW I think there is a reason the 183 is advertised primarily for planetary photography. This is clearly what it will excel at, with its tiny pixels and super high frame rates. But that camera probably won't be the limiting factor when shooting Messier and Caldwell objects and if you bin 2x2 you have a sensor 4.8 micron pixels and a 60,000 electron full well which can just about frame Andromeda with a 80/400 refractor. Not bad at all.
Cheers,
Dimitris
