Sensor analysis QHYCCD 294MPro

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cboillo
Posts: 3
Joined: Sun Sep 12, 2021 9:20 pm

Sensor analysis QHYCCD 294MPro

#1

Post by cboillo »

HI there and thanks a lot for this wonderful software.
I just acquired a QHYCCD 294M Pro and wanted to run the sensor analysis with it.
I did it after the sunset (can't do it during the day because it says it's too bright) and this is the values I got. They are a bit different from their website (higher fullwell, e/ADU and read noise) :
MONO 16 QHY.JPG
MONO 16 QHY.JPG (89.11 KiB) Viewed 377 times
Then, tried to did it with my flat panel at its lowest value but could not start as it has to be from 0,1s to 1s and i can get a good histogram at 60ms max :
Capture3.JPG
Capture3.JPG (170.26 KiB) Viewed 377 times
What do you think? Is there a reason why I can't do it with my flat panel? Why do I get different values from Sharpcap that the one in their website?
Thanks a lot
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admin
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Re: Sensor analysis QHYCCD 294MPro

#2

Post by admin »

Hi,

the reason you have slightly different values is that your e/ADU figure for minimum gain has come out a bit high (4.14 - published values are typically just under 4). This value being high scales all the other readings in the analysis by the same factor (read noise, full well, etc).

The e/ADU is measured in the first part of the analysis, so it's worth watching the graph of green crosses in the first stage to check you get a nice straight line - if anything disturbs the illumination levels during that phase then you can get bad results for the e/ADU measurement which transfer to other figures. Also worth checking that image controls like contrast, colour balance (for colour cameras) etc are at their defaults.

The reason that your panel is considered too bright is that the initial exposure is at minimum gain. If that is too short then in later parts of the analysis when high gain settings are measured, the exposure needed may get close to the cameras minimum exposure value. Past experience has indicated that some cameras misbehave (bad frame data) when set to very short exposures, so SharpCap tries to avoid those when performing the analysis.

One approach you could try is putting a sheet of white paper between the light source and the sensor to reduce illumination. More than one sheet if necessary. Alternatively you could reduce the aperture via which light gets to the sensor with a cardboard mask.

cheers,

Robin
cboillo
Posts: 3
Joined: Sun Sep 12, 2021 9:20 pm

Re: Sensor analysis QHYCCD 294MPro

#3

Post by cboillo »

Hi Robin,
Thanks a lot for your detailed answer.
I'm kind of dumb, I forgot that I had ND filters to put in my Aurora flat panel in case it's too bright.
I did it and could reach the perfect light to proceed with the sensor analysis. Light level was exactly the same during all the process, all images controls were at defaut, yet I still see e/ADU slightly higher than 4 (better but still higher).
Would this have a big impact on the smart histogram or not that much?
Many thanks,
Charly
MONO 16 QHY 1309.JPG
MONO 16 QHY 1309.JPG (96.04 KiB) Viewed 368 times
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admin
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Re: Sensor analysis QHYCCD 294MPro

#4

Post by admin »

Hi,

the difference won't have a massive impact - the predictions depend on the read noise squared, so the ~2-3% overestimation of e/ADU and hence read noise will lead to a ~4-6% longer sub-exposure prediction I think, so not a big change.

cheers,

Robin
cboillo
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Joined: Sun Sep 12, 2021 9:20 pm

Re: Sensor analysis QHYCCD 294MPro

#5

Post by cboillo »

Hi Robin,

I wanted to perform another sensor analysis to see if I could get better results but I had many times this kind of line when analyzing the e/adu, which is very strange.
Do you know what can be the issue?
Thank you,
Charly
Capture.JPG
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Re: Sensor analysis QHYCCD 294MPro

#6

Post by admin »

Hi,

looks like you are getting bad image data sometimes leading to the glitches in the graph.

Try tweaking the USB traffic control upwards - zero USB traffic gives the highest performance, but the most chance of glitches. Also try running the camera in still mode to see if that helps.

cheers,

Robin
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