Seonsor Analysis wont finish on QHY183C

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niccoc1603
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Seonsor Analysis wont finish on QHY183C

Post by niccoc1603 » Sat May 11, 2019 7:37 am

I am attempting a sensor analysis on my QHY183C but it always fail at the last step when measuring Relative Gains

no matter what illumination I set in the beginning (I have tried very dark and very bright), it always returns this error message
I try to set an illumination to aim for an exposure of 1-2ms with a gain of 50

Here a video of the entire measuring process:
https://drive.google.com/open?id=1NmK0q ... TQEPJGLBnK


Image

SharpCap 3.2.5986

BlackWikkett
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Re: Seonsor Analysis wont finish on QHY183C

Post by BlackWikkett » Sat May 11, 2019 11:15 am

Not sure if this is relevant but I notice you are using ROI and then using the selection tool. This makes the amount of pixels inside the selection area very small. Try using the camera full resolution and then use the selection tool.

niccoc1603
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Re: Seonsor Analysis wont finish on QHY183C

Post by niccoc1603 » Sat May 11, 2019 2:04 pm

Thanks, I tried several configurations, it makes no difference

BlackWikkett
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Re: Seonsor Analysis wont finish on QHY183C

Post by BlackWikkett » Sat May 11, 2019 5:13 pm

What are you using as a light source?

I've used LED tracing panel successfully for sensor analysis. https://www.amazon.com/gp/product/B01M2 ... UTF8&psc=1 Used this panel along with a T-shirt to defuse the light to create flats. Use the panel on lowest brightness level.

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Re: Seonsor Analysis wont finish on QHY183C

Post by admin » Sat May 11, 2019 7:22 pm

Hi,

Thanks for sharing a video of that, what I can see is that the camera is responding oddly to changes in exposure when trying to perform the last stages of the sensor analysis. You can see that it is oscillating between 200 ms and about 315 ms exposures. The software expects that the difference between the brightness's of those two exposures to be in proportion to the ratio of their lengths, but if you watch the histogram, it more than doubles when the exposure changes.

Basically what is happening is that SharpCap is looking at the brightness of the frame and seeing that it is too dark and increasing the exposure by a proportion that it expects to make the brightness okay, but that change makes it too bright and then it tries to adjust in the other direction and overshoots again.

I think the underlying problem is that your camera is for some reason not responding correctly to exposure changes. It would be interesting if you could spend a little time gradually adjusting the exposure between the two values that SharpCap is using while watching the histogram and seeing if anything unusual happens (for instance does it get markedly brighter at some point when only making a small change in exposure).

Cheers, Robin

niccoc1603
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Re: Seonsor Analysis wont finish on QHY183C

Post by niccoc1603 » Sun May 12, 2019 4:12 am

I think the underlying problem is that your camera is for some reason not responding correctly to exposure changes. It would be interesting if you could spend a little time gradually adjusting the exposure between the two values that SharpCap is using while watching the histogram and seeing if anything unusual happens (for instance does it get markedly brighter at some point when only making a small change in exposure).
I did some tests and there is something weird

291ms
Image

292ms - totally oversaturated
Image

I have no idea what is happening here

niccoc1603
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Re: Seonsor Analysis wont finish on QHY183C

Post by niccoc1603 » Sun May 12, 2019 5:38 am

[UPDATE 1]

OK, setting USB Traffic to 15 solved the issue with exposures
I have no idea what this parameters controls and how it is related to exposure but it did the trick
Image

So my analysis went through and finished, however the results are odd and do not match with manufacturer paramaters https://www.qhyccd.com/index.php?m=cont ... =30&id=137 and manual analysis

SharpCap RN
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QHY RN
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SharpCap GAIN
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QHY GAIN
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Last edited by niccoc1603 on Sun May 12, 2019 8:27 am, edited 3 times in total.

niccoc1603
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Re: Seonsor Analysis wont finish on QHY183C

Post by niccoc1603 » Sun May 12, 2019 8:23 am

[UPDATE 2: SOLVED!]

Set USB Traffic to 0

All worked perfectly!!

Image

Image

Image

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Re: Seonsor Analysis wont finish on QHY183C

Post by admin » Mon May 13, 2019 6:18 pm

The USB traffic control helps determine how hard the camera tries to push the USB system in order to get maximum frame rate. Normally for qhy cameras, you use a low value for maximum performance and high value for stability. On some systems you will find that the very low values because the frames to stop flowing as communication to the camera gets lost. However it's good to hear that by adjusting this parameter you've managed to get everything working as it should.

Cheers, Robin

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