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QHY168c randomized horizontal banding

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#1 bnickeson


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Posted 05 April 2020 - 01:06 PM

I am still trying to get my QHY168c up and running, but ran into issues last week with randomized horizontal banding on every image.  Didn't matter if it was a 5 second frame and focus image or a 5 minute light.  These bands almost appear like interference bands, so I'm guessing they have to do with either USB interference or possibly the power supply?  The camera didn't come with a DC power cord/supply for whatever reason so I had to get one on my own.  The USB is running through a 3.0 hub into a 3.0 jack, but it also has the OAG camera running through the same hub.  Any guesses?  Thanks.





#2 OrionSword


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Posted 06 April 2020 - 03:45 PM

You would need some additional power supplies and USB cables to test with since there are so many varying qualities of such.  If possible get a hold of a linear power supply instead of using the switching types.  I've used several USB cables in my collection and found one that didn't cause banding.


Are you using a QHY power supply or a substitute?


Also experiment with the USB driver settings and see if they help clean it up.

Edited by OrionSword, 06 April 2020 - 05:27 PM.

#3 bnickeson


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Posted 06 April 2020 - 09:00 PM

I'm using a power cable bought off of Amazon that I believe QHY recommended since they didn't provide a DC power cord.  I'll just have to try swapping out different USB configurations and power setups to figure out a cause.  

#4 1DegreeN


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Posted 06 April 2020 - 10:13 PM

Do you see the same banding on darks? I'm not suggesting you calibrate them out but if the problem is present on darks too then its easier to troubleshoot and you can set the camera and laptop up on a bench and test systematically. Personally I'd be suspicious of the USB hub, I think its always advisable to connect these cameras direct to the computer. Re the power supply, I don't think QHY provide one themselves but their vendors would normally bundle a third party power supply with the camera. I've tried my 168C with 2 different but ordinary 12V adapters, currently powering it via a Pegasus PPB which in turn is powered by one of those adapters. The camera is rated at 4A, my vendor bundled a 6A adapter, and via the PPB I've noticed that the camera appears to be capped around 2A. I've never seen banding on my 168C, but I've always had it connected directly to the computer.

#5 t-ara-fan



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Posted 06 April 2020 - 10:24 PM

  Any guesses?  Thanks.


I doubt very much that USB noise (data corruption) would cause this problem.  USB has error detection built in. USB *might* cause noise on the power supply if cables are tightly wrapped.


What kind of power supply are you using?  Are you powering the camera from 12V, or just over the USB3 port?  As mentioned by OrionSword, a linear supply is better because it has lower noise than a "brick" switcher.  This supply is what AstroPhysics sells with their mounts, I have THREE of them (mount, camera/focuser/USB hub/ guider, and dew heater). 


Speaking of which, was your dew heater running. They are very noisy.


I would see if it happens with darks, makes testing easier. Strip the system down / shut off stuff you don't need, and see what happens.

Edited by t-ara-fan, 06 April 2020 - 10:24 PM.

#6 dghent



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Posted 07 April 2020 - 01:13 PM

The logic board in these cameras are powered from the 5V DC conductors on the USB cable. The 12V DC external power source is for the TEC, as well as for powering a filter wheel on mono cameras if one is connected via the 4-pin connector to the camera. So I would be pretty surprised if quality of the external 12V power supply would impact things here.


You don't mention what software you're using, so I'm going to assume that you're using the QHY ASCOM driver.


Make sure of some things:

1. That the QHY USB driver is updated

2. That the ASCOM driver itself is updated


Try some things:

1. In the settings window for the ASCOM driver, there might be a control for "USB speed" or "USB traffic" or along those lines. Try decreasing the slider to see if that results in improved image quality.

2. See if there is any difference running the USB directly into your PC rather than through the hub. This would help eliminate whether the hub (or other cabling) is at issue here.

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#7 bnickeson


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Posted 10 April 2020 - 08:27 PM

Thanks for the suggestions everyone!  Power source for 12V is directly to a 12V battery, nothing is run through the mount or through any sort of inverter or power supply.  A couple days ago I completely set up my rig indoors as I normally would outside and tried to figure out the issue.  Unfortunately (or fortunately) I wasn't able to replicate the problem and everything with the camera was working perfectly.  Dark frames looked exactly like they should and the (very short) light frames I tried worked fine as well.  


I will, however, start plugging the camera USB directly into the computer rather than through a hub just to avoid any potential traffic issues.


If I encounter the issue in the future at least I'll have several suggestions to work though!

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