Cooled CMOS Cameras - Cool Down and Warm Up

Startrek (Martin) · #1 11-01-2021, 01:52 PM

I’m just wondering how many folk warm up their cameras after an imaging session ? I use APT with my 2600MC and always warm it back up to 0C from the operational temperature of -15C before disconnecting the camera ( as advised by APT and ZWO )
They mention the camera can go into thermal shock ?

Appreciate any comments in regards to the above

Thanks

glend (Glen) · #2 11-01-2021, 03:01 PM

I always used to warm up my ASI1600, using SGP warm up cycle, as part of the shut down sequence. It could run while I parked the scope and closed up the observatory. I did this for years. As I understand it, the thermal shock was mostly related to the mounting of the TEC to the Sensor, and TECs do not equalise gradually without power regulation and air flow to the heatsink. For what it's worth, I usually ran at -17C, in other words, if you have deep cooling you might as well use it.
I used a higher warm up end point temperature, depending in the Night time temp but often 12C, on the basis that shut off at lower temp could encourage condensation.

Startrek (Martin) · #3 11-01-2021, 03:38 PM

Glen
Thanks for your comments
My new 2600MC has anti dew heater to nullify dew , ice and condensation from forming on the sensor surface or chamber. It’s a 5watt polyimide heater which completely covers the protective window. The dew heater can be switched on or off in the Ascom driver set up ( check box ) I leave mine on by default and never had an issue through winter , spring and summer
The older ZWO cooled cameras ( 2019 and before ) never had this feature and suffered from dew or moisture forming on the sensor ( eg ZWOASI071MC)
Thanks
Martin

multiweb (Marc) · #4 11-01-2021, 03:42 PM

With my QHY9 I go down to -20c absolute. Depending how hot ambient is in summer I'll go 10c for 15min, then 0c, then -10c and -20c. In winter if it's very cold already I don't bother. I keep an eye on the TEC power%. That gives me a good indication where I'm at. I rarely go over 40% all year round.

glend (Glen) · #5 11-01-2021, 05:23 PM

Quote:

Originally Posted by Startrek

Glen
Thanks for your comments
My new 2600MC has anti dew heater to nullify dew , ice and condensation from forming on the sensor surface or chamber. It’s a 5watt polyimide heater which completely covers the protective window. The dew heater can be switched on or off in the Ascom driver set up ( check box ) I leave mine on by default and never had an issue through winter , spring and summer
The older ZWO cooled cameras ( 2019 and before ) never had this feature and suffered from dew or moisture forming on the sensor ( eg ZWOASI071MC)
Thanks
Martin

Martin, my comment on condensation related to potential condensation on the camera body not on the sensor or in the sensor chamber (which is protected by dessicant and sealed). Btw, ZWO did offer a heater on its cameras, which could be retrofitted to the original ASI1600 going back to mid-2016. The heater element was adhesive, encircling the sensor window. I has this heater on my 1600 and never had a problem with fogging; in fact it worked so well it prevented filter fogging in the filter wheel.

Startrek (Martin) · #6 11-01-2021, 06:07 PM

Quote:

Originally Posted by glend

Martin, my comment on condensation related to potential condensation on the camera body not on the sensor or in the sensor chamber (which is protected by dessicant and sealed). Btw, ZWO did offer a heater on its cameras, which could be retrofitted to the original ASI1600 going back to mid-2016. The heater element was adhesive, encircling the sensor window. I has this heater on my 1600 and never had a problem with fogging; in fact it worked so well it prevented filter fogging in the filter wheel.

Thanks Glen
So a retro heater kit was offered as a part no
I wonder how many folk bought one ( apart from yourself )
I’ve seen so many comments on CN and IIS in the past and present about condensation, fog, ice , dew , moisture in general on the older ZWO cooled cameras ?
Oh well you were a happy customer
Cheers

AstroApprentice (Jason) · #7 11-01-2021, 09:09 PM

ZWO sensor heater:
https://www.bintel.com.au/product/zw...v=322b26af01d5

gregbradley · #8 12-01-2021, 11:34 AM

This notion of sensors getting thermal shock is an old controversial point.

It was brought up when Apogee cameras used a very slow cooldown and slow warm up routine. It was painful. It took 30 minutes to cool down a 16803 sensor.

If you got a power failure in the middle of the night and an imaging run it meant an hour delay. 30 minutes for warm up plus another 30 minutes of cooldown.

It often meant I missed getting dusk flats unless you remembered to start the camera up an hour before dusk. Watching the light levels fade whilst the camera inched slowly down in temperature was annoying to say the least.

When challenged about the need for this as no other camera makers required it the response was the owners background in aerospace and how thermal shock was a design requirement in that industry.

But there is no evidence of thermal shock from other camera makers and my Proline is now nearly 12 years old and no evidence of thermal shock.

So my advice is to ignore that requirement if it causes problems.
If you want to follow that thermal shock procedure then know its most likely not needed. The only caution here is that the above was about CCD sensors not CMOS. I have no reason to think there would be a massive difference as these CMOS sensors are digital cameras sensors meant to be used in a range of temperatures and I am not aware of any recommendation from the major camera makers to be careful of taking a camera from inside a warm room to outside in a cold environment.

Has anyone seen one?

Greg.

Camelopardalis (Dunk) · #9 12-01-2021, 07:39 PM

I'm not convinced there's the concept of thermal shock with current CMOS cameras. Here's why:

If I change the target temperature of my QHY upwards (i.e. warmer), it just sets cooling power to 0 until it gets to the new temperature and then applies power to maintain it.

You can watch it yourself in Sharpcap or any other software that communicates with your camera's cooler.

gregbradley · #10 13-01-2021, 09:00 AM

Yes that is right. There does not seem to be some delayed progression like Apogee which took 30 minutes to cooldown and the same to warm up (assuming you didn't just power off).

Greg.

The_bluester (Paul) · #11 13-01-2021, 09:31 AM

I am another one who had a ZWO stick on heater, I used it on my ASI294 at one point. Bit of a placebo effect, I can't tell you if it prevented dew on the sensor window I just know I never suffered from it, but I also have not suffered it since I removed it to do something else. I have the window heater switched on on the 2600 at the moment. I could probably go in and turn it off with the temperatures we have now, but I am not inclined to risk wasting part of a night if if dews up when I am in bed, just to find out if it does. I don't get enough imaging time to waste a night for the sake of 5W.

Thermal shock seems to be a "Friend of a friends uncles neighbor" thing as far as anyone who has actually had a problem with it. I ease the 294 down slowly as it has a tiny amount of moisture in the camber (I need to dry the desiccant pills) and bringing it down slowly generally prevents it from forming condensation on the sensor and then icing that up. My ASI2600 I just set -10 and let it cool by itself, and at the end of the night I warm them up in Voyager, which takes maybe 5 minutes. I figure that if it does not cause me any time issues it does no harm to warm them slowly, so I might as well. Voyager does it for me without my intervention so it is as easy as not doing it.

Paulyman (Paul) · #12 15-01-2021, 07:00 PM

I’ve found that if I am using my zwo183 with the native driver in SGP if I ask it to warm up it does so in a very weird way. It rapidly gets up to 5-10C and then COOLS back down to below zero before slowly heating back up to ambient over 15 minutes. So I don’t bother anymore, if it is going to race up to 10C anyway why let it cool back down, so I just turn it off and let it come to ambient naturally now.

Interestingly my QHY183C does warm up correctly, so I do let it do so over the 15 minute cycle.

denodan (Dennis) · #13 14-03-2021, 09:08 AM

When finished on my QHY163C I just turn cooling off and let camera warm things up. No need to set camera to a warmer temp then turn it off, just turn off cooling and keep camera on, when does not warm up anymore or even I would say match the outside temp then disconnect camera. Does not take long at all

Geochron (Jon) · #14 24-03-2021, 06:05 PM

I'm a little surprised to hear that ZWO recommend warming up prior to disconnecting - my ASI183 manual doesn't seem to mention this and the ASIAir auto shutdown procedure just shuts everything down asap as far as I know, irrespective of any cooling underway?

RobF (Rob) · #15 24-03-2021, 07:02 PM

Quote:

Originally Posted by The_bluester

I am another one who had a ZWO stick on heater, I used it on my ASI294 at one point. Bit of a placebo effect, I can't tell you if it prevented dew on the sensor window I just know I never suffered from it, but I also have not suffered it since I removed it to do something else. I have the window heater switched on on the 2600 at the moment. I could probably go in and turn it off with the temperatures we have now, but I am not inclined to risk wasting part of a night if if dews up when I am in bed, just to find out if it does. I don't get enough imaging time to waste a night for the sake of 5W.

Thermal shock seems to be a "Friend of a friends uncles neighbor" thing as far as anyone who has actually had a problem with it. I ease the 294 down slowly as it has a tiny amount of moisture in the camber (I need to dry the desiccant pills) and bringing it down slowly generally prevents it from forming condensation on the sensor and then icing that up. My ASI2600 I just set -10 and let it cool by itself, and at the end of the night I warm them up in Voyager, which takes maybe 5 minutes. I figure that if it does not cause me any time issues it does no harm to warm them slowly, so I might as well. Voyager does it for me without my intervention so it is as easy as not doing it.

Yes, very occasionally have had bit of icing in the QHY9 if cool down too rapidly, so step it down over 10 mins, but not obsessive about warm up. Usually program it in Sequence Generator as an automatic process - if I'm in bed then no time lost letting it do its thing at astronomical twilight for a warm up. Don't do it religiously if pulling down earlier in the night.