I note that Nasim on this site has done a review of the Z lens in question, and seems to find it useable for astronomy, and also suggests that the F mount with the FTZ adapter is not going to be as accurate, at least in AF, and considers the new lens natively sharper too, it seems.
Focus by wire lenses cannot have a scale coupled to the manual focus ring, but in my limited experience, the mechanically coupled ones may not be all that accurate anyway. I have read that when you zoom in the finder on the Z it can be quite noisy, but that this can be improved with settings.
https://photographylife.com/reviews/nikon-z-20mm-f1-8-s
Anyway, if you haven't read the review, and maybe if none of the real experts on this see this thread, I wonder if you could get a response by commenting there. I think the article comments are more active than the forums.
