True confession time:
At the many apartments that I had when I lived in NYC, one constant fixture near a window was a telescope. There's lots of light pollution in NYC, so a clear view of the sky is pretty much impossible, but the telescope was rarely pointed at the sky, it was always pointed at other buildings, and I always spotted many other people doing the same thing.
It's people watching... Nothing wrong with it... That's my story and I'm sticking with it.
I people didn't want to be watched, they'd close the blinds.
