I am using an 8" SCT, mostly doing prime if I am taking pictures of the moon or stars/nebulae. As for planetary obs/shots, I'll be using various eyepieces and barlows.
I know that there are some people already doing that on their balconies and ledges where its deep enuff to put potted plants and not fall over. If pple complain then so be it, wanna stomp me go ahead. The police can come and check to affirm that I am not taking them. I got more interesting thing to look at. Most of the time, it'll be the pier there, except on clear nights, then i'll mount all my barang barang and pple can see a rocket launcher mounted on window ledge. And if I wanna peek at them, I wouldnt make it so obvious as to put on the window ledge literally screaming at them that I am looking at them loh. If you get what I mean.
Not sure about you but I like to take pictures of the moon, and planets. Clouds, have to pick a clear night loh. Light clouds are fine. Daytime not interested cos nothing to see except if I wanna do solar obs during the morning. That is why I need a good solid pier, so I can mount a good tracking/GOTO mount and have my scope automatically track the objects.
So I can conclude that its a NO to window ledge mounting?