@Signma88 Thanks! I tried editing the config files of kerbol. Changing all settings containing brightness/luminosity from 1 to 0.1. One of those settings was set to 0.89999 and I also changed it to 0.1. After these changes luminosity was very low in vessel view or eva (as expected) but map view was completely unaffected.
Could you give me a hint for where I should look to change the luminosity in map view.