Siril Stack Multiple Nights

[johneta]

Hi
Can anyone help me with a brief rundown of stacking multiple nights with Siril.

I have just started to use it, and use the premade scripts, and stack with 'preprocessing  No Darks'
It works well and I like it, but I'm having trouble figuring how to use different flats on different nights

Thanks

[bottletopburly]

You stack the final stack from each night I’m sure I have written it down somewhere will see if I can find it can’t remember off the top of my head .

Edited July 21, 2020 by bottletopburly

[johneta]

Great, thanks. I appreciate it

[bottletopburly]

3 hours ago, johneta said:

Great, thanks. I appreciate it

 Try this if I have got it right ,Every stacking session gives you a stacked fits file ,add a number to fits file name  1,2 etc so you know what files what   , you create a folder and store these fits files you want to merge , then in registration tick match stars  make sure the working directory path is pointing to folder with fits files you want to stack , then go to stacking tab and select go stack , that’s it you’ll be left with a single fits file of all sessions .

[johneta]

Do you mean - if I have 3 nights, I will have 3 stacked images. Then I should stack those final 3 together?
If so, doesnt that miss out on some of the benefits of stacking heaps of images (Sigma rejection etc).

So I might have 30 lights from each night. So each 30 images is stacked into 1 image, then stack those 3 together.
Wouldnt stacking all 90 together somehow be better?

[bottletopburly]

After each stacking session Your left with. Stacked Il fits  image ,it’s each final result you stack together , you’ve already applied sigma tacking etc to get the stacked fit , I found it to work very well , you could also use sirillic to process and stack all data rather than use the scripts , tutorial below .

10 hours ago, johneta said:

Do you mean - if I have 3 nights, I will have 3 stacked images. Then I should stack those final 3 together?
If so, doesnt that miss out on some of the benefits of stacking heaps of images (Sigma rejection etc).

So I might have 30 lights from each night. So each 30 images is stacked into 1 image, then stack those 3 together.
Wouldnt stacking all 90 together somehow be better?

http://download.startools.org/Siril with Sirilic.pdf

 

Edited July 22, 2020 by bottletopburly

[Seelive]

Providing you have sufficient images in each nights stack for the sigma rejection to do its job, then the resulting set of stacks can just be average stacked.  I have found that resulting noise of a sigma stacked image decreases as expected as the number of individual images increases BUT only up to a point, after that, the final image noise level flattens out or even increases.  I tend to break a large number of images (even those taken in the same session) into separate stacks of no more than 20 to 30 images ( I try to keep each stack with about the same number of individual images), sigma stack those and then average stack the separate sigma stacks.  That way I get a resulting image with a noise level the same as if I had just average stacked all the images in one go but without the satellite trails, hot pixels etc.

[johneta]

Thanks very much seelive and bottletopburly. I will look into both these ideas. I'm interested in the concept of stacking medium size bunches of images. Ive never done that before. Always thought, the more the merrier.

In the meantime I went ahead and did this....    I stacked the 3 sessions separately and ended up with 3 result images which I didnt use. I went back and put all the pp_light.... images from each stack into a new folder.
I renamed the files by getting rid of the 'pp_' bit. Leaving them as just 'light...' etc. 

Then I stacked all those images with the script "no darks, no flats, no bias" thinking that they had already had those applied to them individually. Seemed to work well and I was happy with the result.

It was a pretty clunky way to do it, so I will look into your ideas.
Thanks again