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Questions on camera warming and cooling

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#1 bluesilver

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Posted 23 July 2021 - 10:43 PM

Hi,  I just have a few questions in regards to the cooling and warming settings on a ZWO ASI260MC

I am using APT,  and i see that you can cool the camera to -20,  that part is fairly straight forward i think,  I think about -10 works fairly well for this camera and for where i am.

 

The question is that there is also a warming option to set also,  i am just curious to find out what temperature i should be aiming to set this at?

I am coming from a DSLR,  so things are quiet a bit different all around.

Is there a ball park figure that i should be looking to set this warming temperature at?

 

The other question is,  should i be setting the camera up and having it cool down a few hours before i start imaging?

 

What i have been doing previously with my setup is,  I setup all my gear about a hour or two hours before the sun goes down,  have all the dew heaters on.

Should i be letting this camera run idle so to speak for a few hours like the rest of my setup to allow it to be cooled to the set temperature or is it not really needed with these cameras?

It might be a silly question as the camera is going to be outside anyway,  just thought i would ask as i am just starting out with these dedicated cameras.

Any advice is appreciated.

Thanks.

 

 

 

 



#2 AhBok

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Posted 23 July 2021 - 10:51 PM

When using APT, I set up the warming with similar parameters as cooling except, I set the warming to about 2 degrees C below ambient. Lately, I’ve been using an ASIAIR pro which simply lets the camera’s driver handle cooling and warming (which is much quicker for both). I’m considering strongly setting warming and cooling steps in APT to 0 and letting the driver control cooling and warming steps.

#3 bluesilver

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Posted 23 July 2021 - 11:09 PM

Interesting that you set it 2 degrees below ambient.

I guess it all depends on what the ambient temperature is

Here where i am, our temperature gets pretty much down to between -3 to 0 degrees c 

So gets quiet cool,   so was just really trying to find an ideal temperature to set the warming at

Would something like 5 degrees c be a good starting point?



#4 DaveB

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Posted 23 July 2021 - 11:10 PM

I use SGP, but it has similar parameters. I just set the warmup temperature to 20C and set the warmup time to 10 minutes. It is almost always cooler than 20C, even in the summer, so it never reaches that. It will not heat up the camera to 20C, it just targets the cooldown rate based on how warm it's supposed to get, and over how long. It will slowly warm up until it reaches ambient, and at that point the camera temperature stays steady and the cooler is basically turned off.



#5 dswtan

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Posted 23 July 2021 - 11:24 PM

On warming, I'm in the camp that says this is a cargo cult thing you can ignore, unless the manufacturer specifies otherwise in the manual.

 

On cooling, no you don't have to have the camera cooler running for hours. It will reach a stable temperature within a couple of minutes, and stay there. 

 

You won't harm anything by doing either though, if you feel better for it. 



#6 bluesilver

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Posted 23 July 2021 - 11:48 PM

Thanks ,  appreciated,

Good to know.

Do you also have to warm back up the camera before shutting it down?

I would imaging it would go through a thermal shock if just shut of straight away after the imaging session.

Just a thought.



#7 dswtan

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Posted 24 July 2021 - 01:42 AM

I would imaging it would go through a thermal shock if just shut of straight away after the imaging session.

Do whatever makes you happy (and what the manual says, per camera), but where is the “shock”? The camera will naturally warm up to ambient. There is enough mass in the system for this to take a few minutes. A “shock” would if you dunk it in warm water after it’s just been frozen. If you do that though, you have other problems. ;-)

 

There is no “shock” by just switching off the cooler.

 

Examples of actual thermal shock: https://en.wikipedia...l_shock_failure



#8 TOMDEY

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Posted 24 July 2021 - 03:31 AM

Most high-end (amateur) CCD and CMOS cameras take around half an hour to stabilize.

 

Cooler reduces thermal noise, which is good. Even more important is temperature uniformity across the chip and stability. Finger Lakes Instrumentation (FLI) was one of the first to introduce accurate thermostatically-controlled temperature monitoring and display, monitored right at the chip. I lower the setting so that my cooler runs around an 80% duty cycle. This provides an excess cooling capacity margin. Without that, it could creep above and your calibration frames would be meaningless. Cooling the outside of your camera (typically integral fan) is what carries the operational entropy heat away... which is also important. Cryo cooling is the professional standard, especially on infrared cameras. There are also mini cryo refrigeration units, which are astonishingly compact and very expensive. You will recognize these cameras by their heft and especially cost. One little camera (about the size of an FLI Microline)... go for $500K, or even double that. We used and marveled over them at work. The cooling units were subject to failure. They dumped a lot of operational heat into the outside environment, so even that had to be actively piped away. Add to all that, cryo cooling can manifest electrons that ~get stuck~ in the photosites, and then have to be flushed out by warming the entire camera, which gets very messy and stress the hardware, shutting operations down for an hour or a night. Here's some of the plumbing I cobbled together for my ~Roof Cam~ that has an old FLI KAF 16803 on the inside.    Tom

Attached Thumbnails

  • 37.1 Tom's Roof Cam with chiller lid.jpg


#9 Alex McConahay

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Posted 24 July 2021 - 08:47 AM

Do whatever makes you happy (and what the manual says, per camera), but where is the “shock”? The camera will naturally warm up to ambient. There is enough mass in the system for this to take a few minutes. A “shock” would if you dunk it in warm water after it’s just been frozen. If you do that though, you have other problems. ;-)

 

There is no “shock” by just switching off the cooler.

 

Examples of actual thermal shock: https://en.wikipedia...l_shock_failure

Actually, there is a shock. Whether it matters or not is another question. 

 

The way the Peltier Cooler works is to absorb the heat from the imaging sensor to the attached Peltier chip. Then with the aid of electricity, transfer from one side of the Peltier chip (the cooled side)  to the hot side. This hot side, another plate, that then radiates the heat away. (That hot side of the chip is usually attached to a heat sink which further radiates the heat away.)

 

It is quite possible that the hot side of the chip is very much hotter than the cooled side (the side next to the imaging chip). Hot enough that it is uncomfortable to touch. But, as long as the electricity is on, the heat from the hot side does not transfer back to the cool side. Flip the chip off, and the heat RUSHES back to the cool side, and back to the imaging chip. So, there is a rapid change in temperature on the imaging chip. It had been sitting at maybe minus 20 and now gets a rush of heat that was significantly ABOVE ambient. It is not as if the difference is between the chip temperature and ambient. It is that the difference between the hot side of the Peltier chip and the cooled side is particularly great. 

 

What "warming" does on your camera is not "warm" the chip, but just gradually reduce the cooling power so that the difference between the cold side and the hot is not so much that any great heat rushes back to the cold side when the power cuts off completely. 

 

Now, does this matter? I don't know. I've gone for years with no apparent thermal cracking on my chip. Of course, I usually cool back to at least 0 degrees. Sometimes that takes it back to ambient, but often ambient is above that temperature. But, even though I am careful not to shut down without "warm up," there have been times where power has failed or something such that the camera shut down without warmup. And, again, as far as I know I have not damaged the chip. And this issue has come up repeatedly on CN, with very few (any?) reports of damaged chips. 

 

Alex


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