Stacking in SIRIL / SIRILIC with slightly different focal lengths

Dear all,

as someone, who uses zoom telephotolenses for astro, I was wondering how Siril will behave, if I am stacking data of the same camera with somewhat different focal lengths.

Unless I use the lens fully zoomed in or out, I will probably not have the same zoom down to the last millimeter focal length every night. Will this result in problems with registering and stacking, especially in multi-night sessions?


It is supposed to work, the global star registration can rotate and scale images. Be careful to select the reference image as one for which you prefer the framing because others will be cropped to it.

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In my experience, it worked great up to version 0.99.6.

All later versions may very well fail depending on your difference in focal lengths. I posted a recent thread on this very topic.

My personal workaround is to perform all duties apart from registration with the latest version (, and register with 0.99.6 via a virtual desktop.

Inconvenient but effective.


No. It fails if images have not same size.

This is now fixed in master.

Care to elaborate?

The bug you noticed is now fixed in the development version.

So, you’re saying it will be fixed in the next release, then?

yes, or if you don’t want to wait you can use the development version, which requires compiling it. It is documented here, even for windows.


Thanks - I’ll wait for the next release.

FWIW, I went ahead and compiled 0.99.11, and as claimed, it appears the registration issue is indeed fixed.

Thanks for remedying this.