first the lens : 70mm.
manual exposure. I bit underexpose (what I didn't do enough here)
60 pictures, handheld. But tripod would be safer for sure.
4 horizontal series. Allways take care to have superposed parts from one to the next picture.
After that, just use PhotoMerge. That's it. The composition is completely handled by the soft !
I just had to work on some parts to avoid under or over exposition.