A couple of thoughts. Moving so slowly it could have been a balloon that was lit.
Ten years ago there was a story in this area about a UFO at night out in the western end of the county. The cops went out and reported they could see it. They watched it and then went to where it was hovering over. It was a person flying a kite with lights.
Sometimes it’s just people having fun. A little spice of life.
The silent object was ... traveling only about 20 mph.
At which altitude?