Does anyone use Siril?

[han59]

40 minutes ago, AstroMuni said:

My reckoning is that if your original image was captured in 16bit then any further processing can be done in 16bit. Its not like we are adding more info at that stage. But I am also not that close to understanding this.

The bit depth increases with stacking.   If you combine 2 pixels of value 101 and 102 you get 101.5. How do you want to store that? In 16 bit your image will show strange pattern in grey level. Especially because  faint nebula are in the low range of your 16 bit.  Nebula will look like this (without the numbers)

 

 

[AstroMuni]

13 hours ago, han59 said:

Especially because  faint nebula are in the low range of your 16 bit. 

Thanks for the clear explanation 👍

As most of us image from our backyards in less than ideal bortle skies, I am not sure how much more detail we would get by adding the extra bits

Edited October 21, 2021 by AstroMuni

[han59]

The light pollution will not make a difference. Note it will only effect nebula. Just try it. As soon you say layers in faint part of nebula, you know you have to switch to processing in floating point.

 

Just one more remark:

The only reason why you don't see layers in the 8 bit display or 8 bit jpeg is that the image is properly stretched. 

Nebula in the sky will increase the ADU's in your camera with only a few ADU's.  Your 16 bit astro image has a huge range. Stars will generate a lot of ADU up to saturation but you nebula will generate maybe 4 ADU's max.  One you stretch the 16 bit (stacked)image, these 4 ADU's are equivalent to 2 bit or 4 levels.  After stretching the 16 bit image to 0 ... 255  your nebula has maybe levels 0, 4, 8, 12  and 16 and nothing between. So the nebula will appear as having layers.  If you would process in floating point values,  the nebula will have any value between 0 and 16 and the nebula appear as being smooth.

Han