I have an idea for a cool Earth-pointing amateur experiment that could be done through the cupola windows of the ISS. All of them. It would be simple (and not look like the first photo below).
Are there rough drawings of the cupola with approximate dimensions? It looks like it is a round window with six trapezoidal windows around it. I just need an estimate of the sizes of the round and trapezoidal windows, and the 3D offset and inclination of one of the trapezoids. It doesn't need to be very accurate, but right now it's hard to tell from wide-angle photos.
I've included some reference images below of the cupola as viewed from from inside and outside.
below: Astronaut Don Pettit and some cameras completely obscuring this view of the cupola aboard the ISS. From the Smithsonian article How Astronauts Take Such Beautiful Photographs in Space.
below: Unobstructed but wide-angle distorted view of the cupola, from Popular Science. There are six, equally spaced trapezoidal windows, although it is difficult to tell in this image due to the fish-eye distortion.
below: (From left) Expedition 40/41 crew members Alexander Gerst, Reid Wiseman and Max Suraev peer out of the cupola. From blogs.nasa.gov. There are more exterior views of the cupola in this question.