Problem with Day/Night Cycle

Hello every body.

I have a big problem with my day nightcycle. The night ist not realy dark. I think its not a problem with my Blueprint, becouse I made a BP for Day Nightcycle and when I saw thats not so dark (Black texture with stars) I start a new Project and use only a tutorial I found in the Internet.

In both projects I have the same problem. In the nightcycle the sky is not realy black. Its only a Darknes like early in the morning.

What can be wrong?

I use Version 4.21.1

P.S. Sorry for the bad english, but my motherlanguge is german. But I hope here is someone hwo can understand my problem :o

Two things related. Big one: turn off the auto exposure, Small one: turn off the eye adaption.