Siril Background Extraction with a lot of nebulosity

[FenderGreg]

Hi,

I know generally with Siril you generate your grid in background extraction and take off any which may have nebulosity but what if there is more nebulosity than background?

 

I’ve had a go at NGC6888 last night and the area it is in has a lot of nebulosity. I’ve had a go at using background extraction but don’t know if I’ve used it effectively enough or if I’ve killed off the background a bit.

Any pointers would help, should I process without background extraction?

 

cheers

[ONIKKINEN]

If you have a very busy image like this one you shouldn't use the automatic grid thing since it will definitely place some samplers where you wouldn't want to put them. You will want to manually place some samplers on the least worst places around the image. Realistically all of the samplers in this case will be on nebulosity since all of the image is nebulosity, so some will probably be removed. Experiment with the smoothing function and see what works best.

As an example i might place samplers like below (although it would be easier to tell the best positions from raw data):

You might not need this many samplers either. Really it takes a bit of trial and error to get the best out of.

[FenderGreg]

Oh so you can place them almost random. I realised you don’t have to generate a grid but wasn’t sure if you needed to draw one in a similar way.

i will give it a go though I’m feeling I need some more data to really get the whispy detail alongside NGC 6888.

thanks