Superbias not so super??

[Skipper Billy]

I am getting my library of calibration files together for the forthcoming season and I thought I would try the Superbias routine in Pixinsight. To my eyes it has made the standard master bias look worse (standard on left - superbias on the right) default settings used.

Any ideas or comments??

 

[wxsatuser]

Looks like the super bias is posterized, may be a resampling or conversion problem.

[jiberjaber]

How many frames make up the bias you are comparing with the super-bias? I think I made my super-bias out of about 300 frames and I don't recall there being much difference other than progression of what could already be seen.

[blinky]

I had the same problem and reverted back to standard bias

[Ouroboros]

@Skipper Billy Isn’t the point of a super bias to better model the fixed pattern noise?  So I’m just wondering whether it might look worse, but actually do a better job at correcting the light and other frames.  I guess the only way to see is to process with and without. Just a thought. 

[david_taurus83]

That looks normal. My DSLR bias looks similar if I Superbias it.

[Laurin Dave]

Hi  Skipper

As Jiberjaber says how many bias frames did you use?   I normally use 120  for bias and superbias and it works fine but to test I've just made a master bias with 25 frames and it pixelates and looks similar to yours when Superbias is applied..  

Below are my stretched Bias (top) and Superbias  with 120 frames.  16200 sensor.

HTH

Dave

 

[Skipper Billy]

Thanks all.

The master bias are from just 25 subs - that's what I usually take for a master bias as my download speed is very slow ~30 seconds per sub.

I will try both bias frames in a real world processing situation (when we get some darkness!) and see if there is an appreciable difference.

I might also try with 200 subs and see if that makes a difference.

It was the posterized look that made me ask the question.

 

[Jkulin]

Hi David,

I have always used superbias's and they are definitely smoother when compared to a master bias, I take 100 images for when I do my bias's: -

Master bias

Superbias

So just as a matter of course, I create the sueprbias.

HTH