QHY MiniCam 8 and integrated filter wheel

[FEObs]

I purchased this camera to run on my WO Zenithstar 61ii which rides atop my TV101is.

In doing Sensor Analysis with SharpCap 4.1.13332.0 2025-05-20 with a Pegasus Flat Panel, everything runs perfectly.
However, the final results seem odd to me...everything looks flatlined.

That is, all data results are horizontal.

Picture in word docx below.
Advice?

Thanks

Jimmy

QHY-MiniCam8-sensor-run2.docx

(336.53 KiB) Downloaded 32 times

[admin]

Hi Jimmy,

based on that graph, I would say that the most likely thing going on is that the gain adjustment being made by the analysis procedure is having no effect whatsoever. However, even that doesn't quite work as the full well depth is roughly in the right range for an IMX585 at minimum gain, but the read noise is much lower than expected for that setup.

Does the gain control on the camera have any effect when you adjust it? Does the image get brighter when turning it up and dimmer when turning it down? Are there 3 separate gain controls for R/G/B showing on your camera? Some QHY cameras have these instead of a single gain control, although this *should* be dealt with by the analysis. Does your camera have a read mode selection? Could it be in HDR mode which might explain the oddly low read noise?

cheers,

Robin

[FEObs]

Hi Robin

The read mode is set for Linearity HDR Mode.
(see below explanation from QHY) Otherwise we are stuck in 12 bit mode?
How should I set up Sensor Analysis in SharpCap with this camera? QHY says in 12 bit, may encounter colour issues.
Thanks
Jimmy

Linearity HDR Mode

The native ADC of the IMX585 sensor is 12-bit. Compared to 16-bit, the 12-bit depth offers fewer bits, resulting in a relatively narrower dynamic range, which may lead to issues such as insufficient color gradation and potential information loss. During the product development of miniCAM8, QHYCCD merged high and low gain to extend the data to 16-bit. However, since this 16-bit depth is not native, a sudden shift in linearity might occur, affecting the smooth transition in images. To address this, QHYCCD developed the “Linearity HDR” mode, which uses an algorithm-based approach to correct image linearity through software, ensuring smoother transitions and richer color representation.

In the “Linearity HDR” mode, the full well is 46 ke-, while the read noise is only 1.0e-; the dynamic range reaches up to 46,300:1, equivalent to 93 dB or 15.5 stops.

[FEObs]

Hi Robin
Extra bit I forgot.
In Nina I used the sensor anslysis to determine best exposure. After measurements the answer was:
Exposure..Infinity

Hahaha

[FEObs]

Hi Robin
I changed the Linearity HDR read mode off and substitutes FULL RESOLUTION.
SharpCap preformed sensor analysis perfectly....in process.
I opened The Brain and Sensor Data and it was there.
(see attatchedments)
I am hoping for a clear night so I can get some PPEC in and Focus run.
Thanks for your help.
Jimmy

QHYminiCam8M in 12 bit
Gain Value, Relative Gain, e/ADU, Read Noise, FWD (e)
0, 1, 13.328375, 7.9875593, 54593.0234375
10, 1.4165627, 9.408955, 6.6517005, 38539.078125
20, 1.9952134, 6.6801753, 5.8243356, 27361.998046875
30, 2.831027, 4.7079644, 5.1929164, 19283.822265625
40, 3.978441, 3.3501503, 4.832365, 13722.2158203125
50, 5.6656866, 2.352473, 4.5125084, 9635.7294921875
60, 8.015161, 1.6628956, 4.197879, 6811.22021484375
70, 11.410614, 1.1680682, 3.9870377, 4784.4072265625
80, 16.350208, 0.8151807, 1.0689186, 3338.980224609375
90, 23.17393, 0.57514524, 1.0037432, 2355.794921875
100, 32.781136, 0.4065867, 0.94924027, 1665.379150390625
110, 45.921967, 0.29023963, 0.92409116, 1188.821533203125
120, 64.81308, 0.2056433, 0.89025635, 842.31494140625
130, 92.01182, 0.14485504, 0.85992324, 593.3262329101562
140, 129.0504, 0.10328039, 0.83581895, 423.0364685058594
150, 182.0009, 0.073232464, 0.815611, 299.9601745605469
160, 255.14867, 0.052237682, 0.800732, 213.96554565429688
170, 347.75757, 0.03832663, 0.8211609, 156.98587036132812
175, 451.51602, 0.029519163, 0.75145847, 120.91049194335938

[admin]

Hi,

glad you got it sorted - that graph looks much more typical. I wonder if the special 'Linearity HDR' mode has a fixed gain (which SharpCap doesn't know about) - that would explain the gain control doing nothing.

I guess that NINA is not happy with the completely flat data in the original profile - I must admit that I'm not quite sure how SharpCap would recommend based on that data either - will have to look!

cheers,

Robin

[FEObs]

Thanks Robin
I have sent the data to QHY letting them know Linearity HDR read mode does not compute in SharpCap and ergo Nina.
I will post response when I get it.

I am also unsure if that successfull analysis is reporting 12 bit or 16.

My understanding is the QHY MiniCam8 is native 12 bit, but in Linearity HDR mode, and algorithm is used to translate that to report 16 so the full well capacity of 56,000+ is reported.
My thinking is, the translation occurs after the data is received by SharpCap but the data that gets used is the 12 bit, not the interpolated data.

Stay tuned. Thanks

[admin]

Hi,

the first set of data you posted in the word document from HDR mode is a 16 bit mode, while the second analysis is showing values for a 12 bit mode - just divide the FWD readout for any gain by the e/ADU value. You will get 4096 for a 12 bit mode, 16384 for 14 and 65536 for 16 bit (or close to those values).

I think that the HDR mode is combining two different 12 bit readouts from the camera (with and without HCG) into a single 16 bit readout - that happens before the data gets to SharpCap, so SharpCap sees the data as 16 bit.

cheers,

Robin