Big issue on all QHY294M ?


Big issue on all QHY294M ?
« on: November 27, 2020, 10:52:14 AM »

I was looking to order a new QHY294M ; however it seems there is a huge inconsistency between the measurments you provide on the QHY294M page ( https://www.qhyccd.com/index.php?m=content&c=index&a=show&catid=94&id=9&cut=1 ) and the measurments some people got on the QHY294M that they received. We are discussing it on the french forums here : https://www.webastro.net/forums/topic/187214-qhy294mm/page/4/

In 11M mode, everything seems good :)

In 47M mode, the graph on your website shows that the readout noise should be way below 1e- above gain 1500 and the dynamic range still around 12 bits.
However, after multiple measurments using different softwares and two different cameras, it seems that the readout noise is always greater in 47MP mode than in 11MP mode ( around 1.5e- for Gain 3000 in  47MP mode ) and the dynamic range stuck around 10 bits at gain 1500, probably because we only get a 10 bits signal output instead of a 12 bits one.

Is this an issue or the expected behavior ?
Is there a way to get to that juicy 0.7e- readout noise, which would be the only reason i would buy one ?

« Last Edit: November 27, 2020, 11:27:02 AM by Roch »


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Re: Big issue on all QHY294M ?
« Reply #1 on: December 24, 2020, 09:29:43 PM »

          Due to a wrong register setting the previous driver caused the 10bit ADC samples and cause the readout noise meassurement has wrong data. After correct the driver to 12bit ADC mode and the results can be see from the new graph here:


          From this graph it shows the readout noise of the 47MP can not below 1.5e. And even sightly higher than 11mp mode. This is a strange behavior and we are still analyze this results.

Best regards,
Qiu Hongyun
Qiu Hongyun