So i presume that is manual focus like most of their others. How are you finding it is to dial that in for nightscapes and what not without auto focus and setting it to infinity?
most, if not all lenses don't work in AF for shooting dark sky images, and many in my experience require some fiddling and experimenting to get proper focus, most do not get critical focus at infinity. I have rented two different Sigma 20Art lenses, and both of them were a bit different for what was critical. My Batis 18 is pretty easy with the OLED, you can see it at night and after using the SharpStar to help, I know what point is perfect focus for stars.