QHY168C Problems-Changing ROI Changes Gain and White Balance

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Re: QHY168C Problems-Changing ROI Changes Gain and White Balance

Post by admin » Thu May 16, 2019 5:52 pm

Okay, I see what is going on now. Look out for the next update which should have a fix.

Cheers, Robin

eseavey
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Re: QHY168C Problems-Changing ROI Changes Gain and White Balance

Post by eseavey » Sun May 26, 2019 9:24 pm

Robin,
I am wondering if a local vendor needs to lend you a camera. We've been at this for months, and there is still a problem. I admit it doesn't happen as frequent now, which I don't know is worse.
Again, the camera is cooling at full power but the settings show power of 40 (15%).
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Full power cooling after loading profile.txt
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Re: QHY168C Problems-Changing ROI Changes Gain and White Balance

Post by admin » Sun May 26, 2019 9:39 pm

Hi,

Can I ask why you are using a fixed power cooling option instead of setting the target temperature and letting the camera adjust the power automatically? Normally the purpose of cooling is not just to chill the camera in order to reduce thermal noise, but also to keep the sensor at a constant temperature in order to ensure that dark subtraction is as effective as possible. I just wonder if were chasing down an issue with the fixed power cooling when actually the best solution would be to switch to the setpoint cooling instead.

Cheers, Robin

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Re: QHY168C Problems-Changing ROI Changes Gain and White Balance

Post by eseavey » Mon May 27, 2019 3:56 pm

Robin,
When I First turn on the camera I do not want 100% cooling as QHY says it can damage the camera due to temperature shock. So I start at 15% and gradually increase the power and then set the automated temp control. So my concern is camera damage. Also, for framing and focus, it is important that the cooling power does not do the 100% power thing when I change ROI. When I am done imaging, I slowly increase the temperature as well. Also, I switch between my QHY168C and QHY224C as needed, and just want to load the profile to the settings I set it to, not have to think about whether there are settings changed.

Actually, at 1 second exposure and under, Sharpcap seems to want to default to SER filetype, even if FIT is stored in the profile, or last used before shutting down sharpcap. I've accidentally done whole sets if SER captures while I was certain that FIT was in the profile. Now I know Sharpcap changes it, and I need to click AUTO everytime to override the Auto file setting. Small bright planetary nebulae is where the exposure may be around 1 second.

I like not to have to think about hardware/software problems while imaging. I still hear the power briefly go to 100% and then back to the proper setting, as a result of your update. I talked to QHY and they can send you a demo camera. I would be surprised if my camera is the only one with this problem, I just cannot test others.

Thanks

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Re: QHY168C Problems-Changing ROI Changes Gain and White Balance

Post by admin » Mon May 27, 2019 8:46 pm

Hi,

The auto output format setting being on by default can be turned off in the SharpCap settings dialogue.

I will keep thinking about what might be going wrong still with the cooler power in your use case. It's a shame that the auto power control in the qhy SDK doesn't allow for the sort of soft start that you are looking for. I must admit that I've never been desperately convinced by the need to be cautious about fast cooling or warming of CCD or CMOS cameras (when you're testing new versions of the software and it crashes it hardly surprising if the cooler turns off without warning). I've not managed to do any harm to a number of different cooled cameras over the last few years in spite of abusing them in this manner :)

Cheers, Robin

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Re: QHY168C Problems-Changing ROI Changes Gain and White Balance

Post by eseavey » Thu Jun 06, 2019 8:00 pm

Robin,
I downloaded and installed the lastest SDK and Sharpcap and the problem still persists, though not as frequent.
I try to not set the cooler to 100% if there is a large temperature difference between ambient and sensor. Rather be safe than sorry, and QHY mentions it in their manuals. The strange 100% cooling problem happens when I load the profile after reducing the ROI. I can recreate the steps tonight.
Although, would it be an idea to add to the auto settings algorithm to avoid 100% cooler power, and start at 25% if there is a large temperature difference to overcome? Maybe something like >20 degrees difference 25%max cooling, 10-20 degrees 50% max cooling while Tempchange per 10 seconds is greater than 2 degrees. Or something like that to avoid temperature shock. And something similar warming back up.

I would like to mention that I appreciate all your effort maintaining Sharpcap, and the price is extremely low for what it does.

In the QHY manual it says this:
8. How to protect the cooler in QHY174M/C?
The cooler in QHY174M/C can lower the CMOS temperature to a value that's almost 40 degrees centigrade below the ambient temperature. So you need to be careful to avoid thermal shock, which refers to when the cooler's temperature rises or fall dramatically, the cooler is subjected to strong internal stress due to contraction principle. Drastic thermal shock can shorten cooler's service life or permanently break it.

So when you begin to adjust the CMOS temperature, you should avoid setting "Cooler Power" to its maximum value, and you should gradually turn up the "Cooler Power" value. When you turn off the power, if the "Cooler Power" value is very big, you should gradually turn it down before turn off the power.

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Re: QHY168C Problems-Changing ROI Changes Gain and White Balance

Post by admin » Thu Jun 06, 2019 8:42 pm

Hi,

It's definitely getting to be one of those weird things – the last logs that you posted have no evidence of anything untoward as far as I could see (in other words all the values that SharpCap reads from or sends to the camera were the ones I would expect to see). I tried to write some code to let SharpCap read the manual cooling power intermittently and resend the correct value if the value it read from the camera is incorrect, but that didn't seem to work the way I expected (the values read from the camera are often rubbish).

It would be good if the qhy SDK auto power functionality actually took care of the soft start/soft stop recommendation that they have in the documentation, but actually I suspect that they are just using a PI or PID control algorithm to try to keep the temperature at the target based on the feedback from the thermal sensor.

Cheers, Robin

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