I know it is "cheating" to do astronomy through a window and it is something I would never recommend as something to do with a
telescope. A window glass acts as a lens and will distort an image. The higher the magnification and/or the greater the angle of view with respect to the window glass, the worse the distortion. On the other hand, a low magnification instrument, such as 7x or even a 10x
binocular can be used effectively to do some
binocular astronomy through a window. When the temps drop below zero in the winter, I often just turn off the lights in the apartment and place the objectives of my
Nikon 7x50 Prostar as flat as I can against the window glass. No, image quality is not as good as being outside and for seeing the really faint stuff, I will brave the elements. For just scanning the bright stuff, though, it is one heck of a lot warmer in the apartment.