Well I got the window in OK. It was nearly dark when I called it a day. It is not quite waterproof yet as I have a bit of copper flashing to make. It was a very tight squeeze to get down in through it. I used the spirit level to prop it open. It is only supposed to be a ventilator, so it only usually opens about half this much with a little extender chain thing. Fortunately it was possible to take the glass part off to fit the frame as it was about 28kg with the glass in and obviously a lot more care would have been needed with the fragile stuff in place while fitting. It has made a big difference to the mood of the space inside, I am hoping the sun will shine tomorrow morning so we can see how much lighter it is. The sun did come out just for a bit in the evening, so I got a glimpse of that before it got dark. I expect the moon will be fun to watch through it as well. I was surprised that I could still see the tops of the cedar trees between us and the river from inside the house even with a window that almost points straight up.