Dew issue with brand new ZWO ASI071 MC Pro

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Alfredo Beltran
Posts: 4
Joined: Mon Oct 08, 2018 1:37 pm

Dew issue with brand new ZWO ASI071 MC Pro

Post by Alfredo Beltran » Fri Feb 01, 2019 1:31 pm

Hi Sam

I’m having a dew issue with my brand new ZWO ASI071 MC Pro, purchased just in november 2018 from OPT in the Unitated States.

This is how a flat taken last night looks:
E9DDF211-6B9B-4191-8000-0D792B4488D0.jpeg
And the dew pattern is completely consistant with the dew formed on the sensor window (not the front glass):
74299CC6-098C-47D7-809F-56156EEBB9AC.jpeg
Obviously it’s very frustrating having this issue with a new camera which is designed to prevent this from happening. So, why is this happening? The anti dew option is enabled in the Ascom driver.

Should I proceed as stated in this ZWO document?
https://astronomy-imaging-camera.com/ma ... iccant.pdf

Thanks for your help.

Regards,

Alfredo

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chad
Posts: 527
Joined: Thu Feb 09, 2017 4:58 am

Re: Dew issue with brand new ZWO ASI071 MC Pro

Post by chad » Tue Feb 12, 2019 7:12 am

Hi Alfredo,
For the current, I think it is yes. Please follow the Step 8 in the pdf to make a try.
After that, if it still does not work, please let us know.
Thanks
Chad
ZWO Driver Engineer
Location:lon=120.6 lat=31.3
SuZhou China

Alfredo Beltran
Posts: 4
Joined: Mon Oct 08, 2018 1:37 pm

Re: Dew issue with brand new ZWO ASI071 MC Pro

Post by Alfredo Beltran » Thu Feb 14, 2019 2:54 am

Hi

I had to do step 8 twice because first time I had the same dew forming on the sensor. On the second time I thought I had had success because no dew was forming.

I took some deep sky images two nights ago and no dew formed. So far, so good. BUT tonight I’m taking my flats at the very same sensor temperature as during the imaging session (-15C) and the same dew pattern appears again:

3B5001F3-D9F4-42CB-AD0A-227E5988750C.jpeg
Dew on the sensor

And it also shows in the flat:
56907F6D-3908-4089-B7CD-D494BEFE8414.jpeg
Dew pattern shown in the flat

This behavior is not fulfilling the expectations I had when I decided to buy the camera. It is supposed to work well out of the box.

Did I get a faulty unit?

Your help is much appreciated.

Alfredo

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chad
Posts: 527
Joined: Thu Feb 09, 2017 4:58 am

Re: Dew issue with brand new ZWO ASI071 MC Pro

Post by chad » Fri Feb 15, 2019 1:39 am

Hi Alfredo,
Sorry for the problem.
Please try to cool down gradually. For example, if you want to set the temperature to -10 degrees and the ambient temperature is 20 degrees, set the target temperature to 10 degrees first, wait for the temperature reaches and becomes stable, then set the target temperature to 0 degrees, wait agian, after that, and set it to -10 degrees.
If it still does not work, please let me know. I will keep an eye on your problem.
Thanks
Chad
ZWO Driver Engineer
Location:lon=120.6 lat=31.3
SuZhou China

Alfredo Beltran
Posts: 4
Joined: Mon Oct 08, 2018 1:37 pm

Re: Dew issue with brand new ZWO ASI071 MC Pro

Post by Alfredo Beltran » Fri Feb 15, 2019 2:04 am

Chad

I have the camera set to cool down the sensor in 20 minutes from 20C sensor temperature to -15C in SGP. The delta of 35C is within the specification of the camera.

If you don’t mind, please ellaborate on what is the purpose of doing the procedure you’re suggesting, since it is not the procedure intended for the regular use of the camera.

Thanks for your help in advance, which is very appreciated.

Alfredo

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chad
Posts: 527
Joined: Thu Feb 09, 2017 4:58 am

Re: Dew issue with brand new ZWO ASI071 MC Pro

Post by chad » Mon Feb 18, 2019 1:54 am

Hi Alfredo,
If you let it cooling it slowly, does it work?
I don't have the exact reason for it at the moment, because other customers' feedback is that they can do so. We guess that cooling fast, the sensor's temperature would be lower than elsewhere, making it easier to condense. But there is no more specific proof.
Thanks
Chad
ZWO Driver Engineer
Location:lon=120.6 lat=31.3
SuZhou China

Alfredo Beltran
Posts: 4
Joined: Mon Oct 08, 2018 1:37 pm

Re: Dew issue with brand new ZWO ASI071 MC Pro

Post by Alfredo Beltran » Tue Feb 19, 2019 2:46 am

Hi Chad

Thanks for your response.

I tried as you suggested, going from a sensor temperature of 22C to -15C in steps of a delta of 10C every 10 minutes (last step of course was of just -5C).

I did it both on a room temperature of around 20C and outside at a temperature of 11C.

No dew formed!!!

Question would be: which should be the duration to reach -15C from a sensor temperature about 20 or 22C?

Regards,

Alfredo

User avatar
chad
Posts: 527
Joined: Thu Feb 09, 2017 4:58 am

Re: Dew issue with brand new ZWO ASI071 MC Pro

Post by chad » Tue Feb 19, 2019 8:33 am

Hi Alfredo,
Sorry, I'm not sure about that. You know, this slow cooling is still not a good solution for us.
Thanks
Chad
ZWO Driver Engineer
Location:lon=120.6 lat=31.3
SuZhou China

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