Wow, those are some fantastic images. I’ve been imaging untracked/unguided with a DSLR. It has been a bit of challenge getting the comet in the FOV with longer lenses, but well worth the effort. Here are a couple of my images…
Canon 6D, Sigma Art 35mm @ f/2.5, 40 x 8 seconds, ISO 3200
Canon 650D, Sigma DG APO 70-300mm @ f/5.6 & 480mm (FF equiv.), 187 x 1.6sec stacked, ISO 12,800