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I have tried to set CCD's gain=0; offset=126 to take pictures, then RON=47, very noisy~~ the same when offset=110.
Only being set at 116, RON is the same value mentioned in the QHY homepage. 6~7e

Sorry , I forgot to say that QHY6Pro's photo insists of 3 parts: over scan area + object area + optical black area. All of them are showed together.

Hello Dong,

a RON of 6-8 e- is no problem for spectroscopy. I do not understand why it changes with the offset level. This level is normally set by the manufacturer. Check the histogram of the pixel values on your bias frame. It should be smooth and symmetric on both sides with no sharp cut off. If it is cut off at the low side, you should increase your offset level. When you have found a good bias level you should use the same level for all your measurements.

Cheers
Robin

Dear Robin:

Thank you very much! I have just looked at bias and made a screenshot. I do not know if the histogram is good or bad?

Dong .Li

Hello Dong,

The shape of your histogram looks rather strange and it also looks clipped at both the low and high end.
Attached is the histogram of a single 300 sec dark frame from my ATIK 314L+
Can you post the fits of your dark please (as a zipped file)

Cheers
Robin

Hi, Robin:

Now I post ZIP files of both black and bias. And please have a look on them and tell me what is wrong and how and what I shall do.

Thank you~~

Dong .Li

Hello Dong,

I checked your bias frame. The histogram looks fine. I think your histogram plot must be incorrect.

Cheers
Robin

Hello, Robin:

Thank you! This time I open MaxIm and find 2 buttons "histogram and levels", last time it is default as straight-line, so I think that this makes that strange shape; when I change into Gaussian, it becomes a bell-shaped one just like yours, and so does the "levels".
I think that this is the reason that histogram plot is not correct, don't I?

Regards,

Dong . Li