Good info on this channel .....
https://www.youtube.com/watch?v=TVXXPhvwi7U&t=210s
If you can get past Ken's {the angry photographer
} humourous abrasive style there is plenty of no bs advise on the D850 and other cameras. With Nikons f mount you are open to a world of older nikkor lens that could prove cost effective for widefield nightscapes etc.