qhy 168c 0 wonky values

matthew_carlos
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qhy 168c 0 wonky values

Post by matthew_carlos » Thu May 14, 2020 7:01 am

Hi - Getting really wonky values with camera during sensor analysis. First time user here as well....

Any help/recommendations appreciated.

matthew
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SharpCap_SensorAnalysis_QHY168c_May2019(1).jpg
SharpCap_SensorAnalysis_QHY168c_May2019(1).jpg (76.56 KiB) Viewed 455 times

diant
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Re: qhy 168c 0 wonky values

Post by diant » Thu May 14, 2020 8:55 am

Something wrong...
QHY163c is 12-bit camera - your screen tells us 14-bit
Gain range should be 0...500 - your screen tells us 0...900
Full well at gain 200 should be around 1300e - your screen tells us 132e
And so on. Really something wrong here.

PS. My confusion. 168c vs 163c. Excuse me!
Last edited by diant on Fri May 15, 2020 9:51 am, edited 1 time in total.

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Re: qhy 168c 0 wonky values

Post by admin » Thu May 14, 2020 6:41 pm

Hi,

There are a small collection of models of QHY camera that have individual analogue gain controls for the three different colour channels. For these cameras the main gain control is actually a digital gain control (and probably should be left at the minimum value and never touched).

My information was that the models in question were the QHY128C, QHY367C and QHY165C, but I do wonder if the QHY168C may also show the same behaviour – that would certainly explain why the read noise is not changing at all as the gain is altered.

If this does turn out to be the case then I will need to update SharpCap to add the 168C to the cameras that are handled specially to deal with this problem.

It be useful if you could test the sensor analysis again having set the colour balance controls to their minimum value - I think this should hopefully correct the wrong value for the sensor bit depth, which might help us be sure that we are on the track of the correct problem. If you were to then run the analysis yet another time with those control set to perhaps a halfway level, we might also see a lower read noise, again confirming that we are on the track at the right problem.


Cheers, Robin

bwells
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Re: qhy 168c 0 wonky values

Post by bwells » Sun May 17, 2020 4:48 pm

Hey Robin,

I installed and started using your newest SharpCap with my QHY165C. You may recall a year or so ago, we worked on figuring out issues with the sensor analysis for my camera. It appears by your remark in this message that you did add a fix for my camera? Anyway, I will give the newest version a try and see what happen.

Thanks
Bryan

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Re: qhy 168c 0 wonky values

Post by admin » Sun May 17, 2020 8:12 pm

Hi Bryan,

Not quite yet – I have made some changes that I think should fix the analysis of these cameras but they are not all in the latest version on the download page. I have given a couple of test versions to Matthew and it looks like we are homing in on a solution that should work nicely.

Cheers, Robin

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Re: qhy 168c 0 wonky values

Post by admin » Sun May 17, 2020 8:14 pm

If you want though you could try this version which does have all the latest changes in

https://d.sharpcap.co.uk/download.html? ... 3.2.6337.0

Hope that in this version you should see separate red/green/blue gain controls of your camera (which is how these cameras are supposed to work) as well as a digital gain control which I would advise leaving at the lowest setting at all times.

Cheers, Robin

bwells
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Re: qhy 168c 0 wonky values

Post by bwells » Wed May 20, 2020 4:28 pm

Thank you for taking the time to work on this! I will give this a try today or tomorrow.

Last night, I used sensor analysis with the most recent public version of SharpCap, and noticed SharpCap would start the offset at a value of 204. But when the offset is higher than around 65 on your slider, it goes totally white, no matter what the gain is set to, even in total darkness. So it seems the offset range is too big.

I took bias shots for a few gain/offset combinations to center the histogram around 60%:

Gain=150, offset=60
Gain=180, offset=55
Gain=200, offset=50
Gain=220, offset=45
Gain=230, offset=42

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Re: qhy 168c 0 wonky values

Post by admin » Wed May 20, 2020 7:05 pm

Hi,

If the sensor analysis data came from a previous version of SharpCap then it is likely incorrect and doesn't match with the way the current version of SharpCap behaves. If you still see the problem once you have rerun the sensor analysis then I will take a deeper look, but hopefully the problem go away once the analysis data is correct.

Cheers, Robin

bwells
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Re: qhy 168c 0 wonky values

Post by bwells » Thu May 21, 2020 1:19 am

I was unable to get to my telescope tonight, but tomorrow night looks a lot better.

Just so I am clear on how to use the new release, I understand you now have 3 separate gain adjustments, but I am not clear on how that makes the sensor analysis or the smart histogram work correctly for my QHY165C. Can you say just a bit more on how I use the 3 separate gain controls? Or is the main benefit for the sensor analysis to use the three separate gain adjustments to arrive at the correct settings?

Thank you!

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Re: qhy 168c 0 wonky values

Post by bwells » Thu May 21, 2020 12:02 pm

Robin:

Having re-read this entire thread with coffee in my system, I see you said the gain in previous versions of SharpCap was a digital gain, so all adjustments I made or sensor analysis made were to the digital gain rather than the the true (RGB) gains. Now that makes sense. This also helps me better understand the QHY165C user's manual when they talk about RGB channels with respect to gain.

I still have two questions:
  • What about the ASCOM Driver settings I see from EZCap_QT and Astrophotography Tool? The settings dialog for these programs still only have one gain slider that goes from 0-4027. Is it your thinking that this single gain slider is for all 3 channels combined into one slider?
  • What about the offset setting? As I said earlier, even when I set the old digital gain to "1", the offset made the image turn totally white when adjusted just above 60 or so (in SharpCap). Did you make any changes to what the offset slider changes in SharpCap?
Thank you for your support.

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