SiriI(IC) stacking failure


I am having a recurring problem with Sirilic+Siril failing to stack my images.

The script keeps aborting with the same message in red:

***1611336617: running command setext
log: Setting CWD (Current Working Directory) to ‘J:\Astro Pixel Processor\Siril Temp\script’
***1611336617: running command setcpu
***1611336617: running command cd
***1611336617: running command cd
log: Script execution failed.
***1611336617: running command stack
***1611336626: running command cd
***1611336626: running command cd
***1611336626: running command stack
***1611336633: running command cd
***1611336633: running command cd
***1611336633: running command preprocess
***1611336640: running command stack
***seqfile ‘flats.seq’ already exists, not overwriting
***1611336674: running command cd
***1611336674: running command cd
***1611336674: running command preprocess
***1611336680: running command cd
***1611336680: running command cd
***1611336680: running command register
***seqfile ‘images.seq’ already exists, not overwriting
***Script thread exiting

I get the error over and over again. This also applies to the other calibration .seq files too.

I am trying to stack mono Ha files with Darks, Lights, Flats and Darkflats, all placed in their correct fields.

I’ve no idea what has changed, as it worked fine not too long ago.

Any ideas anyone?



Out of interest, I have just manually tried stacking via Siril alone, and the stacked result is a blank light grey image.

I have also successfully stacked the same files with DSS (Sigma clipping and Entropy) and Pixinsight’s WBPP, SubframeSelector and ImageIntegration routines. Both produce expected results.

Looks like there is something going on with Siril, but I don’t know what. I have reinstalled the program, but to no avail.


Hi, which version are you running? There was a problem with some versions this week, but today should be fine.


I am running v0.99.6.

Is this the latest version?

It is the latest released version. Maybe there is something special about your images that makes siril fail then, can you share one please?

Do you want the entire stack and calibration frames?

The individual sub exposures are hi-res and huge (93MB, 47MP QHY294M) and there are a ton of them.

Do you want me to put them on cloud storage?


First check the visualization sliders please.

I’m not sure where to find the visualisation sliders?

I have toggled through the display modes, and usually use the “Histogram” or “Autostretch” modes to get a clear view of the linear stack ready for Background Extraction.

Loading the stack into Startools produces the same blank image.


Am I right in thinking there’s no fix for this then?



After some investigation I have concluded that there is something wrong with the way Siril processes Darkflats.

I re-ran my SirilIC project, this time without the Darkflats and sure enough the stack completed successfully.

With another attempt, I then tried importing the Darkflats into SirilIC’s “Offset” field, and the stack again completed without issue.

For sure there is nothing wrong with my Darkflats, as they were taken with exactly the same settings and time as my flats (obviously with the optics covered), and as previously mentioned, they work perfectly with DSS and Pixinsight.

So, going forward, until this is fixed in Siril, would I be better off stacking my Darkflats as Bias frames, or omitting them altogether?


That would be very strange because I do it very often, and I’m not the only one :).

Maybe that your workflow is not as expected I would say.

Without any images it is very difficult to say something.
But I can say that the way we use the dark flat is the right way. It is just a subtraction.

And how would you go about loading Dark flats into Siril?

My image and calibration files are available, should you wish to test.

Dark flats are subtracted in a first pass to the flat sequence. As we generally do with biases.

Thats’s not what I’m asking - I know darkflats are subtracted from flats. :slight_smile:

Siril’s Pre-processing tab accepts offset, dark and flat master calibration frames. My question is where do you load the master darkflats? The offset field?

I’m sorry but it was my answer. Load a flat sequence and preprocess with your dark flat. Stack to obtain your master flat.
Then load you light sequence and preprocess with this master flat and with your master dark.

Forgive me, but I simply don’t understand how i can “preprocess with my dark flat”.

Here I see 3 fields, offset, dark and flat. How/where do I subtract my dark flats here?

FWIW, here is the successful calibration flow when I load dark flats into the bias/offset field using SirilIC…

Siril Darkflats as Bias OK

And here is the original calibration flow, which always fails with dark flats entered in the dark flats field…

Siril with Darkflats - not OK

I have blinked each and every one of my lights, darks, flats and dark flats in PixInsight to ensure there are no spurious subs where they shouldn’t be. Everything is in order.


But do what I say.

  • Load the flat sequence
  • Preprocess the sequence with your dark flat
  • Stack your preprocessed flat sequence into a master flat
  • Load your dark sequence
  • Stack your master dark
  • Load your light sequence
  • Preprocess with the master flat and master dark.

That’s it.