Flat Setting for 1600MM C

kaos

I just got this camera and the initial tests look great. I am waiting on a coma corrector and was trying to figure out the flat wizard in SGP. I am using a Gerd-Neuman FP to produce my flats. The SGP manual states that "Target mean: This indicates the ADU that you would like to obtain for your flats. For CCDs this value is generally between 20,000 and 40,000. Ideally you want to your flat data to fall in the area where your CCD behaves in a linear manner. You man need to consult your CCD manufacturer to obtain this information, but typically CCDs behave linearly under 40,000 ADU." Since this is a CMOS camera I am not sure what value to enter in the parameter section. Based on the histogram on test images, it looks like the CMOS data is converted into ADUs but I am not sure about this.

Any input into what the parameters in the attached dialog box should be for this camera would be greatly appreciated.

Thanks

Kaos

Sam@ZWO

half of the full well is suggested

so 20,000-30,000 ADU is ok

kaos

That almost sounds like you are suggesting settings that would normally be used in a standard 16-bit CCD. Given the 1600MM is running at 12-bit that would not affect the answer (65536 FW for 16-bit versus 4096 FW for 12 -bit)?

souls33k3r

Funny enough, i have the same question.

The maximum pixel value at the brightest part of the screen (center) should be 1/2 or 1/3 of the maximum achievable value which for the 16bit CCD is 65536 but the value drops to 4096 for a 12bit CMOS sensor.

timn

I've tried a few settings and found 15,000 ADU to be fine. Certainly not higher.

kaos

As best as I can tell from what I have read computers seem to work in multiples of 8bits. I read somewhere that SGP scales the 12bit to 16 bit. So, maybe the 20,000 is correct. But I have read that others seem to get good results with 15K ADU.

If anyone knows differently, I would love to know. Thanks

Kaos

Sam@ZWO

Kaos wrote:
That almost sounds like you are suggesting settings that would normally be used in a standard 16-bit CCD. Given the 1600MM is running at 12-bit that would not affect the answer (65536 FW for 16-bit versus 4096 FW for 12 -bit)?

you are correct because we put the 12bit data in the high 12bit of 16bit