For the sight 1800 is okay, but it is really narrow once it becomes night, so you can adjust night sight to the same amount and if you wish to go beyond 1800, hold Shift and double-click on the value and then you can make it even more. In my project I have locked camera and I set it to 3000 so that it would seem like map has no fog even with transparent tile depth. But it depends on what you seek to achieve.