@ogu1271 & @Ploodovic
Yes the “Sepia Mask” is based on the Black Marble dataset, and it doesn’t even use the highest resolution for this, since the release of MSFS 2020.
In the early tech alphas, night lighting looked completely stunning and nextgen, but somewhere halfway between the alpha and release, the horrible sepia mask was introduced, first making us wonder if it was just a temporary placeholder / bug, but it was truly baffling they stuck to this night tech, and even made it worse in MSFS2024, around 5 years later!
Here’s and old post from October 2020 discussing this, where I also made a youtube video showing that the Sepia Mask is simply a very low-res mask painting the daylight texture into a monochromatic sepia / brown mess, taking no account to what would be illuminated IRL, like roads, parkinglots, and so on, leaving surrounding terrain dark.