problems stacking using master cailb frames

I have a master dark, bias and flat that I want to use with my light frames.

So I set the current working directory to the one with the LIGHTS folder in, went to the Pre-processing tab and entered the filenames of the three master cailb frames and hit “Start pre-processing”

But it has not stacked the lights. All it seems to have done is to generate a new master bias frame (no other master frames). But I already have master calibration frames. What I want is for it to stack.

what am I doing wrong?

Hello, you have probably not opened the sequence you wanted to process. Things in Siril work with sequences, it’s very important to understand how they work. You may have a look at this tutorial, this section in particular: Siril - Manual preprocessing

And preprocessing is only one of the steps, stacking comes after registration which comes after preprocessing.