I made this for a friend, haven't been able to test it. It was designed for a Hawke Eclipse 6-24x50 SF IR scope. the ocular bell diameter is 43mm with an Eye Relief of 96.5 there for this mount has a 44.5mm inner diameter and adjustable lens distance.

The iPhone XS max camera is not round rather oblique and has 2 cameras. I don't own one nor did I bothered on investigating which one is the main or if it uses both of them at the same time so i made the slot a bit bigger so any of them can be aligned to the center.

proceed at your own risk and if it works let me know xD.