synthetic bias - can this be right?!

Software Siril
1

I read the tutorial on how to use synthetic bias as carefully as I could. I took a series of very short exposures and converted those to a sequence and ran the command to spit out the stats. When I paste the results into a spreadsheet this is what I see:

image
image1085×251 9.61 KB

The last two columns I added to record the offset of each shot and then, since the spreadsheet showed me FP values the very last column is the median times 65535 – this set of values looks like nonsense in context.

My question though is this: the median numbers are almost exactly the same as the bias values that I set for each shot (using native camera control driver values through NINA to capture). Is it really plausible that what I should use is offset of “=$offset”??

I’m a bit confused by the last bullet paragraph in the tutorial about determining offset for imaging cameras right before the DSLR section. That seems to imply that you just have to know what the multiplier number is for a 16-bit camera. I have an OGMA AP26CC that I’m working with that has the same sensor as the camera mentioned in that paragraph (ZWO 2600MC, which I think also has the Sony IMX571). Does that mean I should actually use offset of “=10*$offset”??

Thanks for any advice!

2

Hi,

You seem to have set data in 16b, so the stats you are getting are already in 16b, no need to multiply again by 65535. So in your case, seems the median matches the offset setting. Then so be it. You can use =$offset.
Now regarding your question about your sensor, and comparing it to the sensor in the tutorial. The sensor is one thing. And then the driver added by each manufacturer is another. So it could be that for the ZWO version, ZWO made the decision that when you tell its driver to use an setting of 10, it would result in an offset in ADU of 100. While your manufacturer may have chosen that its driver matches setting to the ADU value. So just trust the measurements you’ve done and you’ll be fine.

Cheers

Cecile

3

Very well. Thanks so much for the fast, clear answer, Cecile!