Two generations of telescopes

 
The Canada-France-Hawaii Telescope (left) saw its first night sky in 1979, at which time it was state-of-the-art among astronomical facilities. Our knowledge has since grown and new telescopes use techniques to better ventillate domes, as with the openable sides of Gemini (right), and to better deflect heat, as with new reflective materials used on the outside surfaces instead of white paint.