Post Process through a translucent material ( glass )

I am trying to create a scope. My idea is that i am gonna use post process to make what behind my scope’s glass disappeared and zoom in the camera. But i don’t know how to use post process with translucent material( scope’s glass).

You can’t really use a PP here, because typically, they occupy the whole screen.

It is possible to only use part of the screen, but much more inefficient.

What you can do though, is just make a glass lens, and put it in your scope. The more refraction you have, the more obviously it will be glass.