Looking for information about NVGs.

I'm at a point that I can look at information about a life long goal and that was to buy some type of NVG or thermal optic.

I like the monocular ones but I'm open to others suggestions. If I told you the used it might help also.
I'm looking for something that can be used to walk dogs at but also be able to be used behind a weapon sights. Be really nice of it could hook up to Camara for night photography and astrophotography.

I'm just looking to see what's out there and the cost as I'm sure they are much higher then the last time Looked at this option.