ST-402ME excessive bias frames ADU

I have an ST-402ME camera, S/N 07091974. Recent bias frames have shown that the offset is in excess of 18,000 ADU. Dark frames also measure very high, of course. The table below shows the results of some tests that I have conducted that attempt to illustrate and quantify the problem.
I have made these analyses via Aip4Win on the ST402ME frames. The bias frames all have file names beginning Bias_20211207_233*.fits. The dark frames all have file names beginning Dark_xxs_1x1_-15.2C_20211023_021*.fits. The data for the Dark - Bias frames also seem to yield suspicious results to me.

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Measured Frames Sum of Frames Difference of Frames
in Central Region in Central Region
Avg ADU, SD Avg ADU, SD
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Bias Frames
* ± *=704507 ± 705975 37230, 25.6 -0.34, 22.16
* ± *=710563 ± 712031 37232, 26.3 0.36, 22.15
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Dark Frame - Bias Frame
xx - *=30s_531 - 704507 NA 59.9, 43.9
xx - *=60s_932 - 704507 NA 60.1, 87.3
xx - *=120s_432 - 704507 NA 62.8, 70.0
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The several bias frames that I have made all exhibit featureless noise, so I presume that the problem is not electrical noise that the camera has picked up from nearby devices (of which there is the mount's controller and then one mini computer at distance of about 1m). As I am quite new to working with this kind of CCD camera, I am unsure of what might be done to rectify the problem.

Is there a remedy for this situation? Thank you in advance for any suggestions or help you can provide.

--- Mike

 

Hi Mike.

It would help greatly the Diffraction Limited support staff with a diagnosis if you could reply and upload a copy of an unprocessed bias and dark frame straight from the camera (or supply a public share link to a web hosted folder containing some samples), it’s not really possible to perform a diagnosis from a chart created using another authors software product.

Also, which capture software are you using and what Bit format are using to save the images, i.e. 16 Bit Integer, IEEE 16 Bit Floating Point, etc.

HTH.