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Benefits of cooled sensor?

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#1 Rac19

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Posted 27 May 2018 - 05:12 AM

I have a ZWO ASI1600MC and I am considering whether or not I should think about getting the  cooled version, for DSO imaging. I understand that a cooled sensor means that you have less noise at any particular gain setting. Does the ASI1600MC Pro (i.e cooled) allow higher gain settings? 

 

Another benefit, I believe, is that the sensor temperature is controlled, making it easier to takes darks at the same sensor temperature at lights. Are there any other benefits?



#2 BlackPitchPL

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Posted 27 May 2018 - 05:29 AM

I'm not an expert but you cover most of benefits in cooled CMOS. From what I've read you should see what is avrage temperature in your place and then you can set the CMOS temperature for whole year :).

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#3 OleCuss

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Posted 27 May 2018 - 07:48 AM

A cooled sensor has better SNR.  Better SNR is what imagers strive for.  So you get a cooled sensor to get better images more easily.

 

The exception is Solar, Lunar, and much planetary imaging.  There is so much signal that a great SNR is easy to achieve.  Cooling is still not quite irrelevant, but it is much less valuable.

 

IOW, you might really not see a difference in imaging of Jupiter between a cooled and an un-cooled camera.  If it is a particularly bad sensor you might see a really big difference, but that is just not very likely.

 

And yes, building a darks library can be much easier.



#4 calypsob

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Posted 27 May 2018 - 11:20 AM

I have a ZWO ASI1600MC and I am considering whether or not I should think about getting the  cooled version, for DSO imaging. I understand that a cooled sensor means that you have less noise at any particular gain setting. Does the ASI1600MC Pro (i.e cooled) allow higher gain settings? 

 

Another benefit, I believe, is that the sensor temperature is controlled, making it easier to takes darks at the same sensor temperature at lights. Are there any other benefits?

Cooling lets you keep the thermal heat produced by your sensor regulated.  The heat does not necessarily go away completely but it does stay consistent when cooling is applied.

This allows patterns build up in your data for and outliers remain mostly random. 

When you go to integrate the data and statistically reject outliers, the software can remove noise or other artifacts that should not be in the image to a much higher degree of precision than an uncooled sensor which would be flooded with random noise created by the heat generated from the sensor.

 

 Heat generated by a sensor can be a huge problem because throughout the night if the temps go up, the thermal noise goes up, if temps drop, the thermal noise drops.  This makes it hard to get a good dark frame for dslr users, and if you pick an uncooled 1600 you will be in the same boat.  



#5 pbunn

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Posted 27 May 2018 - 12:05 PM

A cooled sensor is just what it says. It remove a tremendous amount of heat from the sensor. It also regulates the temperature of the sensor.

 

Typically I run my cameras at -20 C (-4F) with an ambient temperature of between 20 and 33 C.

 

The difference in shot noise and read noise at 20C and -20C is roughly 10 times for most sensors.

 

When I used to use a DSLR, I could not image in the hot summer when the night temps were 80F. The camera sensor was usually over 100 F.

 

If you are doing Deep Sky Photography - don 't even consider an uncooled camera.

 

My opinion only based on my experience.



#6 dkeller_nc

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Posted 27 May 2018 - 12:12 PM

To add to Wes' thoughts - Most DSLRs do not have any amp-glow.  That's because most of the read-out circuitry isn't integrated into the imaging chip.  Contrast that with the CMOS chips in dedicated astro-photography cameras.  Most of them are intended for security cameras, where compact design and low-light performance is critical and trumps image quality.  They're also typically designed for video, with relatively fast frame rates.

 

Combine those design goals, and the CMOS sensors we use have read-out circuitry integrated into the chip itself.  The read-out circuitry generates amp-glows, and the amp-glow gets larger as the exposure time lengthens.  That's not a problem for the intended use of these chips where the exposure times are very short.  But for our purposes, it's significant.  If you can hold the temperature of the sensor constant, then you can calibrate out the amp-glow with an identically matching exposure dark-frame.  But the key is "hold the temperature constant", which you can't do with an uncooled astro camera.  So these cameras work quite well in the uncooled version for planetary imaging where exposure times are very short.  Not so much for long-exposure DSO photography.

 

The same problem is present in DSLRs, but not to the extent of surveillance-chip astro cameras since DSLR chips don't typically have amp-glows.


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