Switching the public lighting off

The next two frames are made consequentially around the time that the street lighting is switched off (midnight during the week). Normally the SQM drops then about 0,5 points. It also shows up in these frames as it instantly becomes darker. The frames are completely identical. No Light Pollution filter was used.  There was some light fog in the air but not too much, SQM value around 20,15 before and 20,40 after. Image of Wirtanen, tracked on the comet for 2 minutes.