Orion and the red lights at Kitt Peak Observatory

This photo was taken at the entrance to the Kitt Peak National Observatory. It shows a dazzling scattering of blue stars forming a well-recognizable pattern of the Orion constellation. They contrast sharply with the red lights that illuminate the road leading to the observatory.

Orion over the Kitt Peak Observatory. Source: KPNO/NOIRLab/NSF/AURA/B. Tafreshi

Red lights give the image a certain “otherworldly” character. But this is not a whim of the architect. In fact, they are important in helping to preserve night vision for visitors and employees of the observatory. 

Red light has a little effect on the retina of the human eye trying to adapt to the dark. At the same time, it is bright enough so that people can continue to navigate on the terrain and see what they are doing. That is why red lights are actively used by astronomers during night observations.

The image also shows the McMath-Pierce Solar Telescope. It was built in 1962 and still holds the title of the largest telescope in the world with a fully open aperture.

According to https://noirlab.edu